DeepSeek V4 Flash vs GPT-5.5 Pro
DeepSeek V4 Flash 
GPT-5.5 Pro Verdict
- GPT-5.5 Pro (xhigh) leads on quality: 67.1 vs 62.1.
- DeepSeek V4 Flash (max) is stronger in agents & tools, coding, composite, instruction following, knowledge, long context.
- GPT-5.5 Pro (xhigh) is stronger in maths, reasoning.
- DeepSeek V4 Flash (max) is 258× cheaper ($0.262 vs $67.50 per 1M blended).
- DeepSeek V4 Flash (max) streams 52.9× faster (212 vs 4 tokens per second).
| Metric | DeepSeek V4 Flash (max) | GPT-5.5 Pro (xhigh) |
|---|---|---|
| BenchLeader Index | 62.1 | 67.1 |
| Agents & tools score | 67.0 | – |
| Coding score | 49.1 | – |
| Composite score | 72.8 | – |
| Instruction following score | 76.7 | – |
| Knowledge score | 57.4 | – |
| Long context score | 66.3 | – |
| Maths score | 57.3 | 74.5 |
| Reasoning score | 73.9 | 80.1 |
| Blended price $/M | $0.262 | $67.50 |
| Output speed | 212 tok/s | 4 tok/s |
| Time to first answer | 10.6 s | 3.5 s |
| Context window | 1M | 1.1M |
| FrontierMath Tiers 1–3 | – | 87.7% |
| FrontierMath Tier 4 | – | 78.0% |
| SciCode | 44.9% | – |
| WeirdML | 45.6% | – |
| AA Intelligence Index | 34.5 | – |
| IFBench | 79.2% | – |
| AA-LCR | 79.7% | – |
| AA-Omniscience | -14.3 | – |
| Terminal-Bench Hard | 35.6% | – |
| GPQA Diamond (AA) | 90.8% | – |
| Humanity's Last Exam (AA) | 38.5% | – |
| SciCode (AA) | 50.4% | – |
| τ²-Bench Telecom (AA) | 95.0% | – |
| AIME 2026 | 95.8% | – |
| HMMT February 2026 | 93.9% | – |
| MathArena Apex | 27.1% | – |
| ARC-AGI-1 | – | 95.0% |
| ARC-AGI-2 | – | 84.2% |
| CritPt | 16.6% | 30.6% |
| GDPval (AA) | 47.1% | – |
| τ²-Bench Banking (AA) | 39.4% | – |
| ITBench SRE (AA) | 31.5% | – |
| Analyst Agent (AA) | 25.0% | – |
| LMCA | 35.9% | 53.9% |
| DTBench | 86.4% | 96.0% |
Data as of 2026-09-19. Best configuration of each model; every score links to its source on the model pages.
DeepSeek V4 Flash vs GPT-5.5 Pro: questions
- Is DeepSeek V4 Flash better than GPT-5.5 Pro?
- GPT-5.5 Pro (xhigh) leads on quality: 67.1 vs 62.1. 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, DeepSeek V4 Flash or GPT-5.5 Pro?
- DeepSeek V4 Flash is cheaper: $0.262 against $67.50 per million tokens, blended at three input tokens per output token.
- Which is faster, DeepSeek V4 Flash or GPT-5.5 Pro?
- DeepSeek V4 Flash streams faster: 212 against 4 output tokens per second.
- Which has the larger context window?
- GPT-5.5 Pro accepts more context: 1.1M against 1M tokens.