Claude Sonnet 4.5 Vision vs Gemini 3 Flash Reasoning: which model should you choose?
We compared Claude Sonnet 4.5 Vision and Gemini 3 Flash Reasoning on price, context window and 12 benchmarks. Claude Sonnet 4.5 Vision has the stronger average benchmark score; Gemini 3 Flash Reasoning is cheaper on a blended 3:1 basis.
Claude Sonnet 4.5 Vision
Claude Sonnet 4.5 Vision is a frontier model from Anthropic. It offers a 128,000-token context window, costs $16.99 per million input tokens and $82.33 per million output tokens, and averages 83.8 across the index's benchmark suite.
- Input
- $16.99 / 1M
- Output
- $82.33 / 1M
- Context
- 128,000
- Avg score
- 83.8
- Open weights
- No
Gemini 3 Flash Reasoning
Gemini 3 Flash Reasoning is a frontier model from Google DeepMind. It offers a 128,000-token context window, costs $17.05 per million input tokens and $66.77 per million output tokens, and averages 83.7 across the index's benchmark suite.
- Input
- $17.05 / 1M
- Output
- $66.77 / 1M
- Context
- 128,000
- Avg score
- 83.7
- Open weights
- No
Specification comparison
| Spec | Claude Sonnet 4.5 Vision | Gemini 3 Flash Reasoning | Edge |
|---|---|---|---|
| Input price / 1M | $16.99 | $17.05 | A |
| Output price / 1M | $82.33 | $66.77 | B |
| Context window | 128,000 | 128,000 | Tie |
| Max output | 16,384 | 32,768 | B |
| Average score | 83.8 | 83.7 | A |
| Arena Elo | 1447.6 | 1446.9 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Sonnet 4.5 Vision wins 5, Gemini 3 Flash Reasoning wins 7, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude Sonnet 4.5 Vision | Gemini 3 Flash Reasoning | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 84.8 | 87.2 | 2.4 | Gemini 3 Flash Reasoning |
| GPQA Diamond | 79.6 | 81.8 | 2.2 | Gemini 3 Flash Reasoning |
| SWE-bench Verified | 73.7 | 72.5 | 1.2 | Claude Sonnet 4.5 Vision |
| HumanEval | 87.0 | 86.9 | 0.1 | Claude Sonnet 4.5 Vision |
| MATH-500 | 90.6 | 86.2 | 4.4 | Claude Sonnet 4.5 Vision |
| AIME 2025 | 86.4 | 79.4 | 7.0 | Claude Sonnet 4.5 Vision |
| LiveCodeBench | 76.5 | 77.7 | 1.2 | Gemini 3 Flash Reasoning |
| IFEval | 89.9 | 90.2 | 0.3 | Gemini 3 Flash Reasoning |
| TruthfulQA | 83.7 | 86.6 | 2.9 | Gemini 3 Flash Reasoning |
| HellaSwag | 89.4 | 92.2 | 2.8 | Gemini 3 Flash Reasoning |
| MMMU | 79.7 | 79.8 | 0.1 | Gemini 3 Flash Reasoning |
| Arena Elo | 1447.6 | 1446.9 | 0.7 | Claude Sonnet 4.5 Vision |
Price analysis
On a blended 3:1 input-to-output basis, Claude Sonnet 4.5 Vision costs about $33.33 per million tokens and Gemini 3 Flash Reasoning costs about $29.48. Gemini 3 Flash Reasoning is roughly 12% cheaper than Claude Sonnet 4.5 Vision. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
Both models list a 128,000-token context window. That is enough for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude Sonnet 4.5 Vision wins 5, Gemini 3 Flash Reasoning wins 7, and 0 are tied. On the index average, Claude Sonnet 4.5 Vision leads Gemini 3 Flash Reasoning by 0.1 points (83.8 versus 83.7).
The price picture favours Gemini 3 Flash Reasoning. 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 Claude Sonnet 4.5 Vision for quality-sensitive work and Gemini 3 Flash Reasoning for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.
Choose Claude Sonnet 4.5 Vision if
- You want the higher average benchmark score in this index.
Choose Gemini 3 Flash Reasoning if
- Unit cost matters and you want the cheaper blended price.
- You need the larger 32,768-token output limit.
FAQ
Is Claude Sonnet 4.5 Vision better than Gemini 3 Flash Reasoning?
On the index average, Claude Sonnet 4.5 Vision leads Gemini 3 Flash Reasoning by 0.1 points (83.8 versus 83.7). The better choice depends on price, context and your task. Claude Sonnet 4.5 Vision wins 5 benchmarks, Gemini 3 Flash Reasoning wins 7.
Which is cheaper, Claude Sonnet 4.5 Vision or Gemini 3 Flash Reasoning?
Gemini 3 Flash Reasoning is cheaper on a blended 3:1 basis at about $29.48 per million tokens, versus $33.33 for Claude Sonnet 4.5 Vision.
Which has the larger context window?
Both models list a 128,000-token context window.
Are these models open weights?
Claude Sonnet 4.5 Vision is proprietary; Gemini 3 Flash Reasoning is proprietary.
Which should I choose for production?
If you need a single default, start with Claude Sonnet 4.5 Vision for quality-sensitive work and Gemini 3 Flash Reasoning for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.