Claude Sonnet 5.5 vs GPT-6 Luna
Claude Sonnet 5.5 scores higher on the Models at Work leaderboard (84 vs 66 out of 100). GPT-6 Luna is about 20× cheaper per blended million tokens ($0.20 vs $4). On Artificial Analysis' independent Intelligence Index, Claude Sonnet 5.5 leads 56 to 38.
| Claude Sonnet 5.5 · Anthropic | GPT-6 Luna · OpenAI | |
|---|---|---|
| Leaderboard rank | #4 | #10 |
| Score (0–100) | 84 | 66 |
| Tier | Workhorse | Fast and cheap |
| Price per 1M tokens | $2 in · $10 out | $0.10 in · $0.50 out |
| Context window | 1M | 1M |
| Open weights | No | No |
| Artificial Analysis Intelligence Index | 56 | 38 |
| Best for | Production coding assistants, High-volume agents, Default model for most teams | ChatGPT Free and Go tier, Simple extraction, Cost floors |
Choose Claude Sonnet 5.5 if…
- you need production coding assistants
- you need high-volume agents
- you need default model for most teams
The value pick of the table: second on the index at a fifth of the Opus price, and the fastest of the top five.
Choose GPT-6 Luna if…
- you need chatgpt free and go tier
- you need simple extraction
- you need cost floors
OpenAI's ten-cent model: the one every ChatGPT Free user now has, and the one Haiku users keep comparing themselves to.
What practitioners say
Claude Sonnet 5.5: Less discussed than its siblings because it just works; the October cache-read price cut to $0.10 per million was the news.
Questions people ask
Which is better, Claude Sonnet 5.5 or GPT-6 Luna?
Claude Sonnet 5.5 scores higher on the Models at Work leaderboard (84 vs 66 out of 100). GPT-6 Luna is about 20× cheaper per blended million tokens ($0.20 vs $4). On Artificial Analysis' independent Intelligence Index, Claude Sonnet 5.5 leads 56 to 38.
When should I choose Claude Sonnet 5.5 over GPT-6 Luna?
Choose Claude Sonnet 5.5 for production coding assistants, high-volume agents, default model for most teams. The value pick of the table: second on the index at a fifth of the Opus price, and the fastest of the top five.
When should I choose GPT-6 Luna over Claude Sonnet 5.5?
Choose GPT-6 Luna for chatgpt free and go tier, simple extraction, cost floors. OpenAI's ten-cent model: the one every ChatGPT Free user now has, and the one Haiku users keep comparing themselves to.
Which is cheaper, Claude Sonnet 5.5 or GPT-6 Luna?
Claude Sonnet 5.5 costs $2 per million input tokens and $10 per million output tokens on Anthropic's list price (Claude pricing, read Oct 10, 2026). GPT-6 Luna costs $0.10 per million input tokens and $0.50 per million output tokens on OpenAI's list price (OpenAI API pricing, read Oct 10, 2026).
Scores come from the Models at Work leaderboard: Score is 0 to 100: 50% independent evals normalised within this table, 20% price-performance, 15% practitioner sentiment from Signals and community threads, 15% operational fit (context, speed, availability, open weights). Models within three points are a tie in practice. Vendor-published figures are labelled as such and never counted as independent. Prices are vendor list prices where published; blended figures assume three input tokens per output token.