GPT-5.6 Luna (Medium) vs Step 5 Preview
Which is better for the money: GPT-5.6 Luna (Medium) by OpenAI or Step 5 Preview by StepFun? Intelligence, total benchmark cost, and end-to-end time from Artificial Analysis & other sources, snapshot 2026-10-24.
Trade-off
Verdict
Depends on your budget
Step 5 Preview scores 18.7 points higher (43.7 vs 25.0) but costs 27× as much to run the benchmark ($1190 vs $44.3; premium vs budget cost classes). They are not alternatives at one budget: pick Step 5 Preview when you need intelligence above 25.0, and GPT-5.6 Luna (Medium) when 25.0 is enough.
| Metric | GPT-5.6 Luna (Medium) | Step 5 Preview | Difference |
|---|---|---|---|
| Intelligence (higher is better) | 25.0 | 43.7 | +74.8% Step 5 Preview is 74.8% more intelligent |
| Total AA cost (lower is better) | $44.32 | $1,190.26 | +2585.6% Step 5 Preview is 27× more expensive |
| End-to-end time (lower is better) | 5.82s | 12.06s | +107.2% Step 5 Preview is 107.2% slower |
| Price per 1M tokens (in / out) | $0.20 / $1.20 | $1.00 / $2.70 | |
| Input modalities | Text, Image | Text, Image |
Step 5 Preview vs GPT-5.6 Luna (Medium): 74.8% more intelligence, 2585.6% more cost to run the AA benchmark, and 107.2% slower end-to-end.
Today's Pareto frontier
Against the frontier
- GPT-5.6 Luna (Medium) is off the frontier: at the same or lower cost, GPT-6 Luna (Medium) scores 29.90 for $31.2.
- Step 5 Preview is off the frontier: at the same or lower cost, GPT-6.1 Sol (Max) scores 51.80 for $1082.
GPT-5.6 Luna (Medium)Step 5 PreviewToday's Pareto frontierOpen-weights frontierEvery other model
Matchup
Compare something else
Agents:
Accept: text/markdown or ?format=md returns this page as Markdown. JSON: /api/v1/compare/gpt-5-6-luna-medium/step-5 · Markdown: /api/v1/compare/gpt-5-6-luna-medium/step-5?format=md · llms.txt · agent skill