Grok 4 Fast Reasoning scores 18.4 on the Respan Index (#102), ahead of Qwen3.5 27B at 18.3 (#103). Qwen3.5 27B leads on 2 of the 3 benchmarks both report. Grok 4 Fast Reasoning is 3.0x cheaper per token at list price. Grok 4 Fast Reasoning has the larger context window (2M tokens).
| Benchmark | Grok 4 Fast Reasoning | Qwen3.5 27B |
|---|---|---|
| LMArena Elo | 1405 | 1408 |
| LMArena WebDev (LMArena) | 1159 | 1357 |
| GPQA Diamond | 85.7% | 85.5% |
Higher is better. Each score links to where it was published.
* Estimated: no published scores in that category. How the Respan Index works