DeepSeek V4.1 Flash vs GPT-5.5
DeepSeek V4.1 Flash 
GPT-5.5 Verdict
- GPT-5.5 (xhigh) leads on quality: 67.6 vs 61.9.
- DeepSeek V4.1 Flash (max) is stronger in coding, composite.
- GPT-5.5 (xhigh) is stronger in agents & tools, knowledge, long context, multimodal, reasoning, instruction following, maths.
- DeepSeek V4.1 Flash (max) is 43× cheaper ($0.262 vs $11.25 per 1M blended).
- DeepSeek V4.1 Flash (max) streams 2.7× faster (215 vs 79 tokens per second).
| Metric | DeepSeek V4.1 Flash (max) | GPT-5.5 (xhigh) |
|---|---|---|
| BenchLeader Index | 61.9 | 67.6 |
| Agents & tools score | 59.6 | 62.3 |
| Coding score | 68.9 | 64.6 |
| Composite score | 74.5 | 72.5 |
| Knowledge score | 61.7 | 66.4 |
| Long context score | 68.5 | 68.7 |
| Multimodal score | 61.4 | 64.4 |
| Reasoning score | 69.5 | 79.9 |
| Instruction following score | – | 73.8 |
| Maths score | – | 71.2 |
| Blended price $/M | $0.262 | $11.25 |
| Output speed | 215 tok/s | 79 tok/s |
| Time to first answer | 10.5 s | 52.2 s |
| Context window | 1M | 1.1M |
| FrontierMath Tiers 1–3 | – | 85.3% |
| FrontierMath Tier 4 | – | 72.5% |
| SimpleQA Verified | – | 63.0% |
| OSWorld-Verified 2.0 | – | 13.0% |
| SciCode | – | 56.1% |
| WeirdML | – | 84.9% |
| APEX-Agents | – | 38.5% |
| ProofBench | – | 50.0% |
| GSO-Bench | – | 40.2% |
| LMArena WebDev | 1614 | 1510 |
| LMArena Agent | 4.9 | 5 |
| LiveBench | 81.1% | 80.2% |
| LiveBench Reasoning | 86.7% | 89.7% |
| LiveBench Coding | 80.0% | 82.2% |
| LiveBench Agentic Coding | 77.3% | 54.0% |
| LiveBench Mathematics | 93.3% | 95.9% |
| LiveBench Data Analysis | 79.3% | 81.6% |
| LiveBench Language | 81.2% | 87.4% |
| LiveBench Instruction Following | 70.0% | 70.7% |
| AA Intelligence Index | 39.5 | 38.6 |
| IFBench | – | 75.8% |
| AA-LCR | 84.0% | 84.3% |
| MMMU-Pro | 77.0% | 79.9% |
| AA-Omniscience | -5.3 | 20.5 |
| Terminal-Bench Hard | – | 60.6% |
| GPQA Diamond (AA) | – | 93.5% |
| Humanity's Last Exam (AA) | 39.3% | 45.8% |
| SciCode (AA) | 51.9% | 55.8% |
| τ²-Bench Telecom (AA) | – | 93.9% |
| LiveCodeBench | – | 85.3% |
| MMLU-Pro | – | 88.1% |
| LegalBench | – | 86.5% |
| CorpFin | – | 68.4% |
| TaxEval | – | 75.0% |
| SWE-bench (Vals) | – | 82.6% |
| GPQA Diamond (Vals) | – | 93.2% |
| Vals Index | – | 57.4 |
| AIME 2026 | – | 100.0% |
| HMMT February 2026 | – | 98.5% |
| MathArena Apex | – | 80.2% |
| MCP Atlas | – | 75.3% |
| ARC-AGI-1 | – | 95.0% |
| ARC-AGI-2 | – | 85.0% |
| CritPt | 14.3% | 27.1% |
| GDPval (AA) | 56.6% | 44.8% |
| τ²-Bench Banking (AA) | – | 39.0% |
| ITBench SRE (AA) | – | 45.8% |
| Analyst Agent (AA) | – | 50.0% |
| APEX-Agents (AA) | – | 37.7% |
| CaseLaw v2 | – | 66.2% |
| Code Migration | – | 45.2% |
| Excel Modeling Benchmark | – | 64.5% |
| Finance Agent v2 | – | 51.8% |
| Harvey's Legal Agent Benchmark | – | 3.8% |
| Legal Research Bench | – | 40.4% |
| MedCode | – | 49.1% |
| MedScribe | – | 86.9% |
| MMMU-Pro (Vals) | – | 88.3% |
| MortgageTax | – | 68.8% |
| ProgramBench | – | 0.5% |
| Public Benefits Bench | – | 60.9% |
| SAGE | – | 51.5% |
| SkillsBench | – | 62.2% |
| SREBench | – | 3.8% |
| Tax Agent Bench | – | 60.5% |
| Time Horizon Index: KSP | – | 8.3% |
| Vals Multimodal Index | – | 68.1% |
| Vibe Code Bench v1.1 | – | 69.8% |
| DrugDiscoveryBench | – | 51.6% |
| FORTRESS | – | 16.3% |
| SWE Atlas: Codebase QnA | – | 45.4% |
| SWE Atlas: Refactoring | – | 44.8% |
| SWE Atlas: Test Writing | – | 42.6% |
| EBR-bench | – | 34.3% |
| Mystery Game Puzzles | – | 56.0% |
| PostTrainBench | – | 27.2% |
| DeepSWE | – | 67.0% |
| LMCA | – | 54.3% |
| DTBench | – | 96.0% |
| CursorBench | – | 58.4% |
| ALE-Bench | – | 1943.0 |
| GDP.pdf | – | 26.0% |
Data as of 2026-09-19. Best configuration of each model; every score links to its source on the model pages.
DeepSeek V4.1 Flash vs GPT-5.5: questions
- Is DeepSeek V4.1 Flash better than GPT-5.5?
- GPT-5.5 (xhigh) leads on quality: 67.6 vs 61.9. The BenchLeader Index combines every independent quality benchmark; GPT-5.5 (xhigh) is ahead overall as of 2026-09-19, but check the category scores for your use.
- Is DeepSeek V4.1 Flash better than GPT-5.5 for coding?
- DeepSeek V4.1 Flash scores higher in coding (69 vs 65 on the category index, where 50 is average).
- Is DeepSeek V4.1 Flash better than GPT-5.5 for agentic tasks?
- GPT-5.5 scores higher in agentic tasks (62 vs 60 on the category index, where 50 is average).
- Which is cheaper, DeepSeek V4.1 Flash or GPT-5.5?
- DeepSeek V4.1 Flash is cheaper: $0.262 against $11.25 per million tokens, blended at three input tokens per output token.
- Which is faster, DeepSeek V4.1 Flash or GPT-5.5?
- DeepSeek V4.1 Flash streams faster: 215 against 79 output tokens per second.
- Which has the larger context window?
- GPT-5.5 accepts more context: 1.1M against 1M tokens.