GPT-5.5 (Xhigh) vs GPT-6 Luna (Medium)
Which is better for the money: GPT-5.5 (Xhigh) by OpenAI or GPT-6 Luna (Medium) 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
GPT-5.5 (Xhigh) scores 8.5 points higher (38.4 vs 29.9) but costs 170× as much to run the benchmark ($5294 vs $31.2; flagship vs budget cost classes). They are not alternatives at one budget: pick GPT-5.5 (Xhigh) when you need intelligence above 29.9, and GPT-6 Luna (Medium) when 29.9 is enough.
| Metric | GPT-5.5 (Xhigh) | GPT-6 Luna (Medium) | Difference |
|---|---|---|---|
| Intelligence (higher is better) | 38.4 | 29.9 | −22.1% GPT-6 Luna (Medium) is 22.1% less intelligent |
| Total AA cost (lower is better) | $5,294.36 | $31.17 | −99.4% GPT-6 Luna (Medium) is 99.4% cheaper |
| End-to-end time (lower is better) | 57.73s | Not reported | — not comparable |
| Price per 1M tokens (in / out) | $5.00 / $30.0 | $0.10 / $0.50 | |
| Input modalities | Text, Image | Text, Image |
GPT-6 Luna (Medium) vs GPT-5.5 (Xhigh): 22.1% less intelligence, 99.4% less cost to run the AA benchmark, and end-to-end time not fully reported.
Today's Pareto frontier
Against the frontier
- GPT-5.5 (Xhigh) is off the frontier: at the same or lower cost, Claude Opus 5.5 (Xhigh, Default Fallback) scores 56.00 for $4057.
- GPT-6 Luna (Medium) is on today's frontier: nothing is both smarter and cheaper.
GPT-5.5 (Xhigh)GPT-6 Luna (Medium)Today's Pareto frontierEvery other model
Matchup
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Accept: text/markdown or ?format=md returns this page as Markdown. JSON: /api/v1/compare/gpt-5-5/gpt-6-luna-medium · Markdown: /api/v1/compare/gpt-5-5/gpt-6-luna-medium?format=md · llms.txt · agent skill