DeepSeek: DeepSeek V4 Flash wins on more metrics (5 of 9), but the right pick depends on what you optimize for — see the breakdown below.
| Metric | DeepSeek: DeepSeek V4 Flash | OpenAI: GPT-5.5 |
|---|---|---|
| Intelligence Index | 40.3✓ | — |
| Coding Index | 38.7 | 56.2✓ |
| GPQA Diamond | 89% | 93%✓ |
| Design Arena Elo | 1275 | 1351✓ |
| Speed (tokens/sec) | 71✓ | 39 |
| Latency | 483ms✓ | 3.4s |
| Input price /M | $0.090✓ | $5.00 |
| Output price /M | $0.180✓ | $30.00 |
| Context window | 1.0M | 1.1M✓ |
| Capabilities | ReasoningToolsJSON | ReasoningToolsJSONVision |