GPT-5 vs. GPT-5 (fast): Which is better for coding?

Discussions
1

Hello everyone,

I’m trying to decide which GPT-5 model would be more suitable for my programming tasks, and I’d love to hear your thoughts and experiences.

From what I understand:

  • GPT-5 (fast) offers faster responses with “medium reasoning effort.”
  • The standard GPT-5 provides “high reasoning effort” but is presumably slower.

I’m wondering how this trade-off between speed and reasoning quality applies to coding.

Which model have you found more effective for your daily coding workflow? Any specific examples where one clearly outperformed the other would be super helpful.

Thanks in advance for your advice!

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2

I might be wrong, but I read the dialogs to mean they’re the same model, but Cursor prioritises the fast one at twice the cost of the other.

@condor or am I misunderstanding the differences?

3

They’re both the same model, but the -fast variant uses openAIs priority processing API option, which provides faster speeds for 2x the price.

Likely how this works under the hood is that the priority fast requests go to a separate gpu cluster that has lower utilization, so the requests can be ran faster.

6 Likes
4

In my experience the fast option isn’t any faster, so I wouldn’t waste your credits.

2 Likes
5

That was my experience too. I only ran into AI Busy errors only on that option too.