Gemini 3.5 Flash vs GPT-5.5 Pro
Gemini 3.5 Flash 
GPT-5.5 Pro Verdict
- GPT-5.5 Pro (xhigh) leads on quality: 67.1 vs 64.2.
- Gemini 3.5 Flash (medium) is stronger in agents & tools, coding, composite, human preference, instruction following, knowledge, long context, multimodal.
- GPT-5.5 Pro (xhigh) is stronger in maths, reasoning.
- Gemini 3.5 Flash (medium) is 20× cheaper ($3.38 vs $67.50 per 1M blended).
- Gemini 3.5 Flash (medium) streams 50.3× faster (201 vs 4 tokens per second).
| Metric | Gemini 3.5 Flash (medium) | GPT-5.5 Pro (xhigh) |
|---|---|---|
| BenchLeader Index | 64.2 | 67.1 |
| Agents & tools score | 67.9 | – |
| Coding score | 58.7 | – |
| Composite score | 71.6 | – |
| Human preference score | 67.4 | – |
| Instruction following score | 72.7 | – |
| Knowledge score | 74.1 | – |
| Long context score | 63.5 | – |
| Maths score | 67.2 | 74.5 |
| Multimodal score | 67.5 | – |
| Reasoning score | 64.2 | 80.1 |
| Blended price $/M | $3.38 | $67.50 |
| Output speed | 201 tok/s | 4 tok/s |
| Time to first answer | 13.9 s | 3.5 s |
| Context window | 1.0M | 1.1M |
| FrontierMath Tiers 1–3 | – | 87.7% |
| FrontierMath Tier 4 | – | 78.0% |
| LMArena Text | 1474 | – |
| LMArena Hard Prompts | 1493 | – |
| LMArena Coding | 1502 | – |
| LMArena WebDev | 1492 | – |
| LMArena Vision | 1307 | – |
| AA Intelligence Index | 33.6 | – |
| IFBench | 74.6% | – |
| AA-LCR | 74.3% | – |
| MMMU-Pro | 83.9% | – |
| AA-Omniscience | 20.8 | – |
| Terminal-Bench Hard | 39.4% | – |
| GPQA Diamond (AA) | 92.1% | – |
| Humanity's Last Exam (AA) | 41.3% | – |
| τ²-Bench Telecom (AA) | 95.6% | – |
| ARC-AGI-1 | – | 95.0% |
| ARC-AGI-2 | – | 84.2% |
| CritPt | 10.9% | 30.6% |
| 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% | – |
| LMCA | – | 53.9% |
| DTBench | – | 96.0% |
| GDP.pdf | 14.0% | – |
Data as of 2026-09-19. Best configuration of each model; every score links to its source on the model pages.
Gemini 3.5 Flash vs GPT-5.5 Pro: questions
- Is Gemini 3.5 Flash better than GPT-5.5 Pro?
- GPT-5.5 Pro (xhigh) leads on quality: 67.1 vs 64.2. The BenchLeader Index combines every independent quality benchmark; GPT-5.5 Pro (xhigh) is ahead overall as of 2026-09-19, but check the category scores for your use.
- Which is cheaper, Gemini 3.5 Flash or GPT-5.5 Pro?
- Gemini 3.5 Flash is cheaper: $3.38 against $67.50 per million tokens, blended at three input tokens per output token.
- Which is faster, Gemini 3.5 Flash or GPT-5.5 Pro?
- Gemini 3.5 Flash streams faster: 201 against 4 output tokens per second.
- Which has the larger context window?
- GPT-5.5 Pro accepts more context: 1.1M against 1.0M tokens.