OpenAI vs Vertex AI

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OpenAI vs Vertex AI Comparison
Priyansh Khodiyar's avatar
Priyansh KhodiyarDevRel at CustomGPT.ai

Fact checked and reviewed by Bill Cava

Published: 01.04.2025Updated: 25.04.2025

In this comprehensive guide, we compare OpenAI and Vertex AI across various parameters including features, pricing, performance, and customer support to help you make the best decision for your business needs.

Overview

Welcome to the comparison between OpenAI and Vertex AI!

Here are some unique insights on OpenAI:

OpenAI’s API gives you raw access to GPT-3.5, GPT-4, and more—leaving you to handle embeddings, storage, and retrieval. It’s the most flexible approach, but also the most hands-on.

And here's more information on Vertex AI:

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Enjoy reading and exploring the differences between OpenAI and Vertex AI.

Detailed Feature Comparison

Features
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OpenAI
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Vertex AI
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Data Ingestion & Knowledge Sources
  • OpenAI gives you the GPT brains, but no ready-made pipeline for feeding it your documents—if you want RAG, you’ll build it yourself.
  • The typical recipe: embed your docs with the OpenAI Embeddings API, stash them in a vector DB, then pull back the right chunks at query time.
  • If you’re using Azure, the “Assistants” preview includes a beta File Search tool that accepts uploads for semantic search, though it’s still minimal and in preview.
  • You’re in charge of chunking, indexing, and refreshing docs—there’s no turnkey ingestion service straight from OpenAI.
  • Pulls in both structured and unstructured data straight from Google Cloud Storage, handling files like PDF, HTML, and CSV (Vertex AI Search Overview).
  • Taps into Google’s own web-crawling muscle to fold relevant public website content into your index with minimal fuss (Towards AI Vertex AI Search).
  • Keeps everything current with continuous ingestion and auto-indexing, so your knowledge base never falls out of date.
  • Lets you ingest more than 1,400 file formats—PDF, DOCX, TXT, Markdown, HTML, and many more—via simple drag-and-drop or API.
  • Crawls entire sites through sitemaps and URLs, automatically indexing public help-desk articles, FAQs, and docs.
  • Turns multimedia into text on the fly: YouTube videos, podcasts, and other media are auto-transcribed with built-in OCR and speech-to-text. View Transcription Guide
  • Connects to Google Drive, SharePoint, Notion, Confluence, HubSpot, and more through API connectors or Zapier. See Zapier Connectors
  • Supports both manual uploads and auto-sync retraining, so your knowledge base always stays up to date.
Integrations & Channels
  • OpenAI doesn’t ship Slack bots or website widgets—you wire GPT into those channels yourself (or lean on third-party libraries).
  • The API is flexible enough to run anywhere, but everything is manual—no out-of-the-box UI or integration connectors.
  • Plenty of community and partner options exist (Slack GPT bots, Zapier actions, etc.), yet none are first-party OpenAI products.
  • Bottom line: OpenAI is channel-agnostic—you get the engine and decide where it lives.
  • Ships solid REST APIs and client libraries for weaving Vertex AI into web apps, mobile apps, or enterprise portals (Google Cloud Vertex AI API Docs).
  • Plays nicely with other Google Cloud staples—BigQuery, Dataflow, and more—and even supports low-code connectors via Logic Apps and PowerApps (Google Cloud Connectors).
  • Lets you deploy conversational agents wherever you need them, whether that’s a bespoke front-end or an embedded widget.
  • Embeds easily—a lightweight script or iframe drops the chat widget into any website or mobile app.
  • Offers ready-made hooks for Slack, Microsoft Teams, WhatsApp, Telegram, and Facebook Messenger. Explore API Integrations
  • Connects with 5,000+ apps via Zapier and webhooks to automate your workflows.
  • Supports secure deployments with domain allowlisting and a ChatGPT Plugin for private use cases.
Core Chatbot Features
  • GPT-4 and GPT-3.5 handle multi-turn chat as long as you resend the conversation history; OpenAI doesn’t store “agent memory” for you.
  • Out of the box, GPT has no live data hook—you supply retrieval logic or rely on the model’s built-in knowledge.
  • “Function calling” lets the model trigger your own functions (like a search endpoint), but you still wire up the retrieval flow.
  • The ChatGPT web interface is separate from the API and isn’t brand-customizable or tied to your private data by default.
  • Pairs Vertex AI Search with Vertex AI Conversation to craft answers grounded in your indexed data (Google Developers Blog Vertex AI RAG).
  • Draws on Google’s PaLM 2 or Gemini models for rich, context-aware responses.
  • Handles multi-turn dialogue and keeps track of context so chats stay coherent.
  • Powers retrieval-augmented Q&A with GPT-4 and GPT-3.5 Turbo, keeping answers anchored to your own content.
  • Reduces hallucinations by grounding replies in your data and adding source citations for transparency. Benchmark Details
  • Handles multi-turn, context-aware chats with persistent history and solid conversation management.
  • Speaks 90+ languages, making global rollouts straightforward.
  • Includes extras like lead capture (email collection) and smooth handoff to a human when needed.
Customization & Branding
  • No turnkey chat UI to re-skin—if you want a branded front-end, you’ll build it.
  • System messages help set tone and style, yet a polished white-label chat solution remains a developer project.
  • ChatGPT custom instructions apply only inside ChatGPT itself, not in an embedded widget.
  • In short, branding is all on you—the API focuses purely on text generation, with no theming layer.
  • Lets you tweak UI elements in the Cloud console so your chatbot matches your brand style.
  • Includes settings for custom themes, logos, and domain restrictions when you embed search or chat (Google Cloud Console).
  • Makes it easy to keep branding consistent by tying into your existing design system.
  • Fully white-labels the widget—colors, logos, icons, CSS, everything can match your brand. White-label Options
  • Provides a no-code dashboard to set welcome messages, bot names, and visual themes.
  • Lets you shape the AI’s persona and tone using pre-prompts and system instructions.
  • Uses domain allowlisting to ensure the chatbot appears only on approved sites.
L L M Model Options
  • Choose from GPT-3.5 (including 16k context), GPT-4 (8k / 32k), and newer variants like GPT-4 128k or “GPT-4o.”
  • It’s an OpenAI-only clubhouse—you can’t swap in Anthropic or other providers within their service.
  • Frequent releases bring larger context windows and better models, but you stay locked to the OpenAI ecosystem.
  • No built-in auto-routing between GPT-3.5 and GPT-4—you decide which model to call and when.
  • Connects to Google’s own generative models—PaLM 2, Gemini—and can call external LLMs via API if you prefer (Google Cloud Vertex AI Models).
  • Lets you pick models based on your balance of cost, speed, and quality.
  • Supports prompt-template tweaks so you can steer tone, format, and citation rules.
  • Taps into top models—OpenAI’s GPT-4, GPT-3.5 Turbo, and even Anthropic’s Claude for enterprise needs.
  • Automatically balances cost and performance by picking the right model for each request. Model Selection Details
  • Uses proprietary prompt engineering and retrieval tweaks to return high-quality, citation-backed answers.
  • Handles all model management behind the scenes—no extra API keys or fine-tuning steps for you.
Developer Experience ( A P I & S D Ks)
  • Excellent docs and official libraries (Python, Node.js, more) make hitting ChatCompletion or Embedding endpoints straightforward.
  • You still assemble the full RAG pipeline—indexing, retrieval, and prompt assembly—or lean on frameworks like LangChain.
  • Function calling simplifies prompting, but you’ll write code to store and fetch context data.
  • Vast community examples and tutorials help, but OpenAI doesn’t ship a reference RAG architecture.
  • Offers full REST APIs plus client libraries for Python, Java, JavaScript, and more (Google Cloud Vertex AI SDK).
  • Backs you up with rich docs, sample notebooks, and quick-start guides.
  • Uses Google Cloud IAM for secure API calls and supports CLI tooling for local dev work.
  • Ships a well-documented REST API for creating agents, managing projects, ingesting data, and querying chat. API Documentation
  • Offers open-source SDKs—like the Python customgpt-client—plus Postman collections to speed integration. Open-Source SDK
  • Backs you up with cookbooks, code samples, and step-by-step guides for every skill level.
Integration & Workflow
  • Workflows are DIY: wire the OpenAI API into Slack, websites, CRMs, etc., via custom scripts or third-party tools.
  • Official automation connectors are scarce—Zapier or partner solutions fill the gap.
  • Function calling lets GPT hit your internal APIs, yet you still code the plumbing.
  • Great flexibility for complex use cases, but no turnkey “chatbot in Slack” or “website bubble” from OpenAI itself.
  • Snaps into other GCP services—BigQuery, Dataflow, Cloud Functions—for end-to-end workflows (Google Cloud Architecture).
  • Follows a modular, API-driven design so you can mix search and chat components the way you want.
  • Automates tasks via connectors or custom code to tie into CRMs, ticketing tools, and beyond.
  • Gets you live fast with a low-code dashboard: create a project, add sources, and auto-index content in minutes.
  • Fits existing systems via API calls, webhooks, and Zapier—handy for automating CRM updates, email triggers, and more. Auto-sync Feature
  • Slides into CI/CD pipelines so your knowledge base updates continuously without manual effort.
Performance & Accuracy
  • GPT-4 is top-tier for language tasks, but domain accuracy needs RAG or fine-tuning.
  • Without retrieval, GPT can hallucinate on brand-new or private info outside its training set.
  • A well-built RAG layer delivers high accuracy, but indexing, chunking, and prompt design are on you.
  • Larger models (GPT-4 32k/128k) can add latency, though OpenAI generally scales well under load.
  • Serves answers in milliseconds thanks to Google’s global infrastructure (Google Cloud Vertex AI RAG).
  • Combines semantic and keyword search for strong retrieval accuracy.
  • Adds advanced reranking to cut hallucinations and keep facts straight.
  • Delivers sub-second replies with an optimized pipeline—efficient vector search, smart chunking, and caching.
  • Independent tests rate median answer accuracy at 5/5—outpacing many alternatives. Benchmark Results
  • Always cites sources so users can verify facts on the spot.
  • Maintains speed and accuracy even for massive knowledge bases with tens of millions of words.
Customization & Flexibility ( Behavior & Knowledge)
  • You can fine-tune (GPT-3.5) or craft prompts for style, but real-time knowledge injection happens only through your RAG code.
  • Keeping content fresh means re-embedding, re-fine-tuning, or passing context each call—developer overhead.
  • Tool calling and moderation are powerful but require thoughtful design; no single UI manages persona or knowledge over time.
  • Extremely flexible for general AI work, but lacks a built-in document-management layer for live updates.
  • Gives fine-grained control over indexing—set chunk sizes, metadata tags, and more to shape retrieval (Google Cloud Vertex AI Search).
  • Lets you adjust generation knobs (temperature, max tokens) and craft prompt templates for domain-specific flair.
  • Can slot in custom cognitive skills or open-source models when you need specialized processing.
  • Lets you add, remove, or tweak content on the fly—automatic re-indexing keeps everything current.
  • Shapes agent behavior through system prompts and sample Q&A, ensuring a consistent voice and focus. Learn How to Update Sources
  • Supports multiple agents per account, so different teams can have their own bots.
  • Balances hands-on control with smart defaults—no deep ML expertise required to get tailored behavior.
Pricing & Scalability
  • Pay-as-you-go token billing: GPT-3.5 is cheap (~$0.0015/1K tokens) while GPT-4 costs more (~$0.03-0.06/1K). [OpenAI API Rates]
  • Great for low usage, but bills can spike at scale; rate limits also apply.
  • No flat-rate plan—everything is consumption-based, plus you cover any external hosting (e.g., vector DB). [API Reference]
  • Enterprise contracts unlock higher concurrency, compliance features, and dedicated capacity after a chat with sales.
  • Uses pay-as-you-go pricing—charges for storage, query volume, and model compute—with a free tier to experiment (Google Cloud Pricing).
  • Scales effortlessly on Google’s global backbone, with autoscaling baked in.
  • Add partitions or replicas as traffic grows to keep performance rock-solid.
  • Runs on straightforward subscriptions: Standard (~$99/mo), Premium (~$449/mo), and customizable Enterprise plans.
  • Gives generous limits—Standard covers up to 60 million words per bot, Premium up to 300 million—all at flat monthly rates. View Pricing
  • Handles scaling for you: the managed cloud infra auto-scales with demand, keeping things fast and available.
Security & Privacy
  • API data isn’t used for training and is deleted after 30 days (abuse checks only). [Data Policy]
  • Data is encrypted in transit and at rest; ChatGPT Enterprise adds SOC 2, SSO, and stronger privacy guarantees.
  • Developers must secure user inputs, logs, and compliance (HIPAA, GDPR, etc.) on their side.
  • No built-in access portal for your users—you build auth in your own front-end.
  • Builds on Google Cloud’s security stack—encryption in transit and at rest, plus fine-grained IAM (Google Cloud Compliance).
  • Holds a long list of certifications (SOC, ISO, HIPAA, GDPR) and supports customer-managed encryption keys.
  • Offers options like Private Link and detailed audit logs to satisfy strict enterprise requirements.
  • Protects data in transit with SSL/TLS and at rest with 256-bit AES encryption.
  • Holds SOC 2 Type II certification and complies with GDPR, so your data stays isolated and private. Security Certifications
  • Offers fine-grained access controls—RBAC, two-factor auth, and SSO integration—so only the right people get in.
Observability & Monitoring
  • A basic dashboard tracks monthly token spend and rate limits in the dev portal.
  • No conversation-level analytics—you’ll log Q&A traffic yourself.
  • Status page, error codes, and rate-limit headers help monitor uptime, but no specialized RAG metrics.
  • Large community shares logging setups (Datadog, Splunk, etc.), yet you build the monitoring pipeline.
  • Hooks into Google Cloud Operations Suite for real-time monitoring, logging, and alerting (Google Cloud Monitoring).
  • Includes dashboards for query latency, index health, and resource usage, plus APIs for custom analytics.
  • Lets you export logs and metrics to meet compliance or deep-dive analysis needs.
  • Comes with a real-time analytics dashboard tracking query volumes, token usage, and indexing status.
  • Lets you export logs and metrics via API to plug into third-party monitoring or BI tools. Analytics API
  • Provides detailed insights for troubleshooting and ongoing optimization.
Support & Ecosystem
  • Massive dev community, thorough docs, and code samples—direct support is limited unless you’re on enterprise.
  • Third-party frameworks abound, from Slack GPT bots to LangChain building blocks.
  • OpenAI tackles broad AI tasks (text, speech, images)—RAG is just one of many use cases you can craft.
  • ChatGPT Enterprise adds premium support, success managers, and a compliance-friendly environment.
  • Backed by Google’s enterprise support programs and detailed docs across the Cloud platform (Google Cloud Support).
  • Provides community forums, sample projects, and training via Google Cloud’s dev channels.
  • Benefits from a robust ecosystem of partners and ready-made integrations inside GCP.
  • Supplies rich docs, tutorials, cookbooks, and FAQs to get you started fast. Developer Docs
  • Offers quick email and in-app chat support—Premium and Enterprise plans add dedicated managers and faster SLAs. Enterprise Solutions
  • Benefits from an active user community plus integrations through Zapier and GitHub resources.
Additional Considerations
  • Great when you need maximum freedom to build bespoke AI solutions, or tasks beyond RAG (code gen, creative writing, etc.).
  • Regular model upgrades and bigger context windows keep the tech cutting-edge.
  • Best suited to teams comfortable writing code—near-infinite customization comes with setup complexity.
  • Token pricing is cost-effective at small scale but can climb quickly; maintaining RAG adds ongoing dev effort.
  • Packs hybrid search and reranking that return a factual-consistency score with every answer.
  • Supports public cloud, VPC, or on-prem deployments if you have strict data-residency rules.
  • Gets regular updates as Google pours R&D into RAG and generative AI capabilities.
  • Slashes engineering overhead with an all-in-one RAG platform—no in-house ML team required.
  • Gets you to value quickly: launch a functional AI assistant in minutes.
  • Stays current with ongoing GPT and retrieval improvements, so you’re always on the latest tech.
  • Balances top-tier accuracy with ease of use, perfect for customer-facing or internal knowledge projects.
No- Code Interface & Usability
  • OpenAI alone isn’t no-code for RAG—you’ll code embeddings, retrieval, and the chat UI.
  • The ChatGPT web app is user-friendly, yet you can’t embed it on your site with your data or branding by default.
  • No-code tools like Zapier or Bubble offer partial integrations, but official OpenAI no-code options are minimal.
  • Extremely capable for developers; less so for non-technical teams wanting a self-serve domain chatbot.
  • Offers a Cloud console to manage indexes and search settings, though there’s no full drag-and-drop chatbot builder yet.
  • Low-code connectors (PowerApps, Logic Apps) make basic integrations straightforward for non-devs.
  • The overall experience is solid, but deeper customization still calls for some technical know-how.
  • Offers a wizard-style web dashboard so non-devs can upload content, brand the widget, and monitor performance.
  • Supports drag-and-drop uploads, visual theme editing, and in-browser chatbot testing. User Experience Review
  • Uses role-based access so business users and devs can collaborate smoothly.

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Final Thoughts

We hope you found this comparison of OpenAI vs Vertex AI helpful.

OpenAI is unbeatable for custom workflows if you have the dev muscle. If you’d rather not build retrieval and analytics from scratch, layering a RAG platform like CustomGPT.ai on top can save serious time.

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Priyansh Khodiyar's avatar

Priyansh Khodiyar

DevRel at CustomGPT.ai. Passionate about AI and its applications. Here to help you navigate the world of AI tools and make informed decisions for your business.