Gemini 3 Flash Pro vs GPT-5.1 Vision: which model should you choose?
We compared Gemini 3 Flash Pro and GPT-5.1 Vision on price, context window and 12 benchmarks. Gemini 3 Flash Pro and GPT-5.1 Vision are effectively tied on the index average; GPT-5.1 Vision is cheaper on a blended 3:1 basis.
Gemini 3 Flash Pro
Gemini 3 Flash Pro is a frontier model from Google DeepMind. It offers a 400,000-token context window, costs $17.71 per million input tokens and $86.50 per million output tokens, and averages 84.8 across the index's benchmark suite.
- Input
- $17.71 / 1M
- Output
- $86.50 / 1M
- Context
- 400,000
- Avg score
- 84.8
- Open weights
- No
GPT-5.1 Vision
GPT-5.1 Vision is a frontier model from OpenAI. It offers a 400,000-token context window, costs $17.76 per million input tokens and $80.59 per million output tokens, and averages 84.8 across the index's benchmark suite.
- Input
- $17.76 / 1M
- Output
- $80.59 / 1M
- Context
- 400,000
- Avg score
- 84.8
- Open weights
- No
Specification comparison
| Spec | Gemini 3 Flash Pro | GPT-5.1 Vision | Edge |
|---|---|---|---|
| Input price / 1M | $17.71 | $17.76 | A |
| Output price / 1M | $86.50 | $80.59 | B |
| Context window | 400,000 | 400,000 | Tie |
| Max output | 4,096 | 16,384 | B |
| Average score | 84.8 | 84.8 | Tie |
| Arena Elo | 1469.2 | 1462.4 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Gemini 3 Flash Pro wins 6, GPT-5.1 Vision wins 6, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Gemini 3 Flash Pro | GPT-5.1 Vision | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 87.0 | 85.5 | 1.5 | Gemini 3 Flash Pro |
| GPQA Diamond | 77.7 | 78.7 | 1.0 | GPT-5.1 Vision |
| SWE-bench Verified | 73.3 | 73.6 | 0.3 | GPT-5.1 Vision |
| HumanEval | 89.9 | 89.6 | 0.3 | Gemini 3 Flash Pro |
| MATH-500 | 91.8 | 89.1 | 2.7 | Gemini 3 Flash Pro |
| AIME 2025 | 79.9 | 82.4 | 2.5 | GPT-5.1 Vision |
| LiveCodeBench | 80.2 | 77.8 | 2.4 | Gemini 3 Flash Pro |
| IFEval | 92.8 | 92.7 | 0.1 | Gemini 3 Flash Pro |
| TruthfulQA | 86.2 | 86.9 | 0.7 | GPT-5.1 Vision |
| HellaSwag | 90.6 | 92.1 | 1.5 | GPT-5.1 Vision |
| MMMU | 83.0 | 83.9 | 0.9 | GPT-5.1 Vision |
| Arena Elo | 1469.2 | 1462.4 | 6.8 | Gemini 3 Flash Pro |
Price analysis
On a blended 3:1 input-to-output basis, Gemini 3 Flash Pro costs about $34.91 per million tokens and GPT-5.1 Vision costs about $33.47. GPT-5.1 Vision is roughly 4% cheaper than Gemini 3 Flash Pro. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
Both models list a 400,000-token context window. That is enough for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Gemini 3 Flash Pro wins 6, GPT-5.1 Vision wins 6, and 0 are tied. The two models are effectively tied on the index average at 84.8.
The price picture favours GPT-5.1 Vision. The context picture is effectively a tie. Those two dimensions often matter more than a few benchmark points once a model is good enough for the task.
If you need a single default, start with GPT-5.1 Vision if cost is the constraint and Gemini 3 Flash Pro if context is the constraint. Test both on a sample of your own traffic before committing.
Choose Gemini 3 Flash Pro if
- You prefer Google DeepMind's tooling or already use it.
Choose GPT-5.1 Vision if
- Unit cost matters and you want the cheaper blended price.
- You need the larger 16,384-token output limit.
FAQ
Is Gemini 3 Flash Pro better than GPT-5.1 Vision?
The two models are effectively tied on the index average at 84.8. The better choice depends on price, context and your task. Gemini 3 Flash Pro wins 6 benchmarks, GPT-5.1 Vision wins 6.
Which is cheaper, Gemini 3 Flash Pro or GPT-5.1 Vision?
GPT-5.1 Vision is cheaper on a blended 3:1 basis at about $33.47 per million tokens, versus $34.91 for Gemini 3 Flash Pro.
Which has the larger context window?
Both models list a 400,000-token context window.
Are these models open weights?
Gemini 3 Flash Pro is proprietary; GPT-5.1 Vision is proprietary.
Which should I choose for production?
If you need a single default, start with GPT-5.1 Vision if cost is the constraint and Gemini 3 Flash Pro if context is the constraint. Test both on a sample of your own traffic before committing.