Quick Take

Claude Sonnet 5 (released June 30, 2026) and GPT-5.5 (high) (released April 23, 2026) are top-tier models competing for dominance in the AI landscape. Claude Sonnet 5 excels in output velocity and pricing, while GPT-5.5 (high) demonstrates a broader range of benchmark capabilities and significantly lower latency for the first token.

Benchmark Read

Performance metrics reveal a tight race. Claude Sonnet 5 holds an Intelligence Index of 53.4, slightly edging out GPT-5.5’s 53.1. However, GPT-5.5 (high) maintains a marginal lead in coding (71.6 vs 71.5).

In specialized benchmarks, GPT-5.5 (high) consistently outperforms Claude in GPQA (0.932 vs 0.911), HLE (0.43 vs 0.396), SciCode (0.559 vs 0.536), and LCR (0.733 vs 0.707). GPT-5.5 also provides data for IFBench (0.716), TerminalBench Hard (0.598), and TAU2 (0.929), showcasing its versatility in complex evaluation environments.

Cost and Speed

Cost structures differ significantly between the two providers. Claude Sonnet 5 is the more budget-friendly option, with a blended cost of $6.00/1M tokens compared to GPT-5.5’s $11.25/1M. Claude’s input cost is $3.00/1M and output is $15.00/1M, whereas GPT-5.5 charges $5.00/1M for input and $30.00/1M for output.

Regarding speed, Claude Sonnet 5 delivers a faster output speed of 88.576 tok/s. However, GPT-5.5 (high) is vastly superior in time-to-first-token, clocking in at 12.332s compared to Claude’s 72.504s, making GPT-5.5 feel more responsive for interactive applications.

Best Fit

Claude Sonnet 5 is best suited for high-volume, cost-sensitive tasks where sustained output speed is the primary bottleneck. GPT-5.5 (high) is the preferred choice for developers and researchers who prioritize low-latency interaction and require the highest possible scores on complex scientific and logical benchmarks.