GPT-4o vs Claude 3.5 Sonnet: A 2026 Comparison
GPT-4o and Claude 3.5 Sonnet are the two most-used frontier models in 2026. We benchmarked both across 200+ prompts in 5 categories.
Coding
Claude 3.5 Sonnet wins decisively on multi-file edits and refactoring. GPT-4o is faster but produces code that needs more iteration.
Long-form writing
GPT-4o has the edge for natural, flowing prose. Claude 3.5 Sonnet can feel a touch stiff.
Reasoning & math
Both are close. Claude 3.5 Sonnet is slightly better on multi-step reasoning.
Vision
GPT-4o handles complex images (charts, screenshots) more reliably. Claude 3.5 Sonnet is competitive on natural photos.
Price
GPT-4o: $5/M input. Claude 3.5 Sonnet: $3/M input. Sonnet is 40% cheaper.
Verdict
If you need coding or large context, go with Claude 3.5 Sonnet. If you need vision or natural writing, go with GPT-4o. Or use Westtree’s smart routing to pick the right model per task.