GPT-5.5 Pro vs Claude 3 Haiku

Head-to-head technical comparison of intelligence, capabilities, and API pricing.

GPT-5.5 Pro

OpenAI

AI Mastery Index94.2

LMSYS Arena1350

Technical (MMLU-Pro)94.2%

Cost per 1M Tokens$30

Claude 3 Haiku

Anthropic

AI Mastery Index78.5

LMSYS Arena1180

Technical (MMLU-Pro)75.2%

Cost per 1M Tokens$0.25

Architect's Verdict

When comparing GPT-5.5 Pro and Claude 3 Haiku, GPT-5.5 Pro edges out in overall capabilities according to the AI Mastery Index. However, for cost-sensitive workloads, Claude 3 Haiku offers a more economical API at $0.25 per 1M tokens. Your choice should depend heavily on whether you prioritize raw reasoning (MMLU) or scalable deployment economics.