Z.ai: GLM 5.1 wins on more metrics (6 of 9), but the right pick depends on what you optimize for — see the breakdown below.
| Metric | OpenAI: GPT-5 Codex | Z.ai: GLM 5.1 |
|---|---|---|
| Intelligence Index | 44.6✓ | 43.8 |
| Coding Index | 38.9✓ | 35.8 |
| GPQA Diamond | 84% | 84%✓ |
| Design Arena Elo | 1140 | 1366✓ |
| Speed (tokens/sec) | 74 | 78✓ |
| Latency | 2.8s | 789ms✓ |
| Input price /M | $1.25 | $0.980✓ |
| Output price /M | $10.00 | $3.08✓ |
| Context window | 400K✓ | 203K |
| Capabilities | ReasoningToolsJSONVision | ReasoningToolsJSON |