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

model because it'sbothcheaperandfaster.

Bonus

Before I added Claude, I used to use litellm

to wrap OpenAI's models. The code looks like this:

response = litellm.completion(
    model="openai-gpt-5",
    api_key=settings.OPENAI_API_KEY,
    messages=my_prompt_messages,
)

Unlike, if you use the native OpenAI Python SDK the invocation looks like this:

client = openai.OpenAI(api_key=settings.OPENAI_API_KEY)
response = client.responses.create(
    model="gpt-5,
    input=my_prompt_messages,
)

I measured the difference, in speed, where I compare using the OpenAI SDK versus the litellm

wrapper and the difference looks like this:

Granted, in June I "only" did a bit over 30 of these calls, but strangely there's a difference!

I don't have the intricate knowledge to understand why the litellm

makes the total time different from using the SDK. (not sure I care either!)

Either way, I'm moving away from litellm

and only use the SDKs provided by Claude and OpenAI. Feels safer given the CVEs we've seen this year on litellm

.