If you are choosing an API model today, Gemini 3 Pro Preview and GPT-5.1 are no longer two equally available options. Google says gemini-3-pro-preview shut down on March 9, 2026. OpenAI lists GPT-5.1 as deprecated with an April 1, 2027 shutdown date. An article recommending either as a timeless “best model” would miss the most important buying constraint. Google’s exact model page, OpenAI’s GPT-5.1 reference. OpenAI’s dated retirement notices.
Researched and written by GPT, an AI, from cited primary sources. Recommendations are editorial assessments; no hands-on performance test is claimed. Numerical examples are calculations under stated assumptions.
Sources checked November 3, 2026.
This comparison is useful for understanding older results or moving an existing integration. It is not a comparison of the current Gemini and ChatGPT consumer subscriptions. Their available models, tools and allowances can differ from these API endpoints.
What the historical specifications explain
Gemini 3 Pro Preview accepted text, images, video, audio and PDFs and produced text. Its documented limits were 1,048,576 input tokens and 65,536 output tokens. GPT-5.1 lists text and image input, text output, a 400,000-token context and 128,000 maximum output tokens. Input limits and total context are different quantities; they should not be printed as if they were identical measurements.
That distinction matters for a workflow combining recorded interviews, slides and a long report. Gemini’s direct audio/video support described a different input path from GPT-5.1’s documented modalities. Converting recordings into transcripts changes the pipeline and may discard information. A fair migration test should compare the complete pipeline, including transcription or frame extraction where needed, rather than only the final model call.
Do not budget against a closed endpoint
GPT-5.1’s listed standard rates are $1.25 per million input tokens and $10 per million output tokens, with separate cached-input pricing. Two million uncached input tokens plus 500,000 billed output tokens would calculate to $7.50 before tools, discounts, taxes and retries. That figure is a scenario, not a measured workload or a current price advantage over an unavailable Gemini endpoint. GPT-5.1 pricing and reasoning controls.
A current Google replacement needs its own price and limit check. Google’s current Gemini 3 Pro page points readers toward Gemini 4 Argon. Do not assume a replacement inherits every behavior, price or tool capability of the retired model.
Preserve the task when changing the model
For a research-report workflow, save a representative set of original source files, questions and expected supporting passages. Test whether the replacement identifies the right evidence, distinguishes conflicting sources and admits when an answer is missing. Include a recording whose tone or visual content matters, not only clean text transcripts.
Record exact model IDs, reasoning settings, preprocessing, retrieval steps and tool permissions. GPT-5.1 exposes multiple reasoning settings; an old result with one effort setting is not a guarantee for another. Also record the time a reviewer spends correcting citations or formatting, because a cheaper token bill can hide more manual work.
The practical recommendation is to retain GPT-5.1 only where its remaining lifecycle and verified behavior justify it, while planning a supported successor. Treat Gemini 3 Pro results as historical evidence. Build the next shortlist from endpoints that are available to your account and test them against the same underlying task.
Model references
OpenAI · Model library
GPT-5.1
DeprecatedGPT-5.1 is the exact OpenAI endpoint in the historical comparison and has a published retirement schedule.
Author’s assessment; check the guide’s evidence and limitations.- Access
- API
- Input
- text, image
- Output
- text
- Context window
- 400,000 tokens
Catalog checked . Model specifications do not establish access through a particular app or subscription.
