Claude Opus 5.5 vs Gemini 3.5 Flash
Claude Opus 5.5 
Gemini 3.5 Flash Verdict
- Claude Opus 5.5 (thinking) leads on quality: 70.7 vs 63.9.
- Claude Opus 5.5 (thinking) is stronger in composite, knowledge, long context, multimodal, reasoning.
- Gemini 3.5 Flash (medium) is stronger in agents & tools, coding, human preference, instruction following, maths.
- Gemini 3.5 Flash (medium) is 2.4× cheaper ($3.38 vs $8.00 per 1M blended).
- Gemini 3.5 Flash (medium) streams 4.6× faster (221 vs 48 tokens per second).
| Metric | Claude Opus 5.5 (thinking) | Gemini 3.5 Flash (medium) |
|---|---|---|
| BenchLeader Index | 70.7 | 63.9 |
| Composite score | 95.0 | 70.2 |
| Knowledge score | 85.0 | 73.0 |
| Long context score | 68.5 | 63.2 |
| Multimodal score | 71.9 | 67.2 |
| Reasoning score | 95.0 | 63.4 |
| Agents & tools score | – | 67.9 |
| Coding score | – | 58.7 |
| Human preference score | – | 67.5 |
| Instruction following score | – | 72.7 |
| Maths score | – | 67.2 |
| Blended price $/M | $8.00 | $3.38 |
| Output speed | 48 tok/s | 221 tok/s |
| Time to first answer | 4.2 s | 12.8 s |
| Context window | 1M | 1.0M |
| LMArena Text | – | 1474 |
| LMArena Hard Prompts | – | 1493 |
| LMArena Coding | – | 1502 |
| LMArena WebDev | – | 1492 |
| LMArena Vision | – | 1307 |
| AA Intelligence Index | 57.6 | 33.6 |
| IFBench | – | 74.6% |
| AA-LCR | 84.7% | 74.3% |
| MMMU-Pro | 87.7% | 83.9% |
| AA-Omniscience | 46.4 | 20.8 |
| Terminal-Bench Hard | – | 39.4% |
| GPQA Diamond (AA) | – | 92.1% |
| Humanity's Last Exam (AA) | 61.4% | 41.3% |
| SciCode (AA) | 66.9% | – |
| τ²-Bench Telecom (AA) | – | 95.6% |
| CritPt | 31.7% | 10.9% |
| GDPval (AA) | 67.3% | – |
| LMArena Maths | – | 1478 |
| LMArena Creative Writing | – | 1466 |
| LMArena Instruction Following | – | 1463 |
| LMArena Multi-turn | – | 1476 |
| LMArena Longer Queries | – | 1478 |
| LMArena Document | – | 1461 |
| Surface Evolver Bench | – | 58.1% |
| DeepSWE | – | 37.4% |
| GDP.pdf | – | 14.0% |
| Terminal-Bench 4.0 (AA) | 59.6% | – |
| AutomationBench | 69.5% | – |
| GDP.pdf | 26.2% | – |
| Harvey LAB | 91.2% | – |
| AA-Omniscience: accuracy | 66.2% | 51.0% |
| AA-Omniscience: non-hallucination | 41.4% | 38.2% |
| AA-Briefcase | 1822 | – |
Data as of 2026-09-22. Best configuration of each model; every score links to its source on the model pages.
Claude Opus 5.5 vs Gemini 3.5 Flash: questions
- Is Claude Opus 5.5 better than Gemini 3.5 Flash?
- Claude Opus 5.5 (thinking) leads on quality: 70.7 vs 63.9. The BenchLeader Index combines every independent quality benchmark; Claude Opus 5.5 (thinking) is ahead overall as of 2026-09-22, but check the category scores for your use.
- Which is cheaper, Claude Opus 5.5 or Gemini 3.5 Flash?
- Gemini 3.5 Flash is cheaper: $3.38 against $8.00 per million tokens, blended at three input tokens per output token.
- Which is faster, Claude Opus 5.5 or Gemini 3.5 Flash?
- Gemini 3.5 Flash streams faster: 221 against 48 output tokens per second.
- Which has the larger context window?
- Gemini 3.5 Flash accepts more context: 1.0M against 1M tokens.