Claude Opus is 10x faster than OpenAI GPT 5 at non-streaming completions

This picture summarizes it well: Here on my blog, for this popular blog post I get a lot of comments. 28k blog comments over the years. Some of them are terribly written and hard to understand, so I let AI suggest a rewrite. That code that sends the blog post comment to AI, I actually fire off three times: once with OpenAI gpt-5, once with OpenAI gpt-5-mini, and once with Claude claude-opus-4.8. I use my human eyes and judgement to evaluate the results, and I can tell you they do equally well. Only the slightest differences. The surprising thing is how amazingly slow OpenAI's gpt-5 is! It's nearly 10x slower than claude-opus-4.8. What's up with that!? It's also clear that the latency difference between gpt-5-mini and gpt-5 is significant. At the time of writing, the input token price difference between gpt-5.4 and gpt-5.4-mini is $2.50 compared to $0.75! That's a 3x difference. Conclusion If you're constructing a prompt the API, use Claude. If you have to use OpenAI, consider the mini…