OpenAI: GPT-5.5 vs Z.ai: GLM 5.1
OpenAI: GPT-5.5 wins on more metrics (5 of 9), but the right pick depends on what you optimize for — see the breakdown below.
| Metric | OpenAI: GPT-5.5 | Z.ai: GLM 5.1 |
|---|---|---|
| Intelligence Index | 54.8✓ | 40.2 |
| Coding Index | 74.9✓ | 55.8 |
| GPQA Diamond | 94%✓ | 87% |
| Design Arena Elo | 1300✓ | — |
| Speed (tokens/sec) | 51 | 101✓ |
| Latency | 2.0s | 304ms✓ |
| Input price /M | $5.00 | $0.966✓ |
| Output price /M | $30.00 | $3.04✓ |
| Context window | 1.1M✓ | 203K |
| Capabilities | ReasoningToolsJSONVision | ReasoningToolsJSON |