GLM-5.1 (Reasoning) vs GPT-5.5 Instant (June 2026)
Which is better for the money: GLM-5.1 (Reasoning) by Z AI or GPT-5.5 Instant (June 2026) by OpenAI? Intelligence, total benchmark cost, and end-to-end time from Artificial Analysis & other sources, snapshot 2026-10-26.
Trade-off
Verdict
Depends on your budget
GLM-5.1 (Reasoning) scores 0.1 points higher (26.1 vs 26.0) but costs 1.3× as much to run the benchmark ($1487 vs $1184; both premium class). Pick GLM-5.1 (Reasoning) when the extra intelligence is worth the premium, otherwise GPT-5.5 Instant (June 2026).
| Metric | GLM-5.1 (Reasoning) | GPT-5.5 Instant (June 2026) | Difference |
|---|---|---|---|
| Intelligence (higher is better) | 26.1 | 26.0 | −0.4% GPT-5.5 Instant (June… is 0.4% less intelligent |
| Total AA cost (lower is better) | $1,486.78 | $1,184.34 | −20.3% GPT-5.5 Instant (June… is 20.3% cheaper |
| End-to-end time (lower is better) | 59.15s | 16.68s | −71.8% GPT-5.5 Instant (June… is 71.8% faster |
| Price per 1M tokens (in / out) | $1.28 / $4.07 | $5.00 / $30.0 | |
| Input modalities | Text | Text, Image |
GPT-5.5 Instant (June 2026) vs GLM-5.1 (Reasoning): 0.4% less intelligence, 20.3% less cost to run the AA benchmark, and 71.8% faster end-to-end.
Today's Pareto frontier
Against the frontier
- GLM-5.1 (Reasoning) is off the frontier: at the same or lower cost, GPT-6.1 Sol (Max) scores 51.80 for $1082.
- GPT-5.5 Instant (June 2026) is off the frontier: at the same or lower cost, GPT-6.1 Sol (Max) scores 51.80 for $1082.
GLM-5.1 (Reasoning)GPT-5.5 Instant (June 2026)Today's Pareto frontierOpen-weights frontierEvery other model
Matchup
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