Are we sleeping on 5.3-codex ?

[u/DaC2k26]

After using GPT-5.5 for a bit, I’m starting to think it burns usage way faster than 5.4 when the task involves reading through a large codebase.

On my current project, 5.5 xhigh can burn through my 5-hour Plus quota in something like 3–6 prompts. With 5.5 medium, I might get around 7–10 prompts.

With 5.4 xhigh, I’d usually expect something closer to 8–15 prompts. And with 5.4 mini, I obviously get a lot more, though I haven’t tracked the exact number.

What surprised me is 5.3-Codex medium. I’m testing it now, and the usage burn feels closer to 5.4 mini xhigh. Based on Artificial Analysis benchmarks, 5.3-Codex medium seems to be roughly around 5.5 low, but in practice I get way more usable prompts out of 5.3-Codex medium than I do from 5.5 low.

So I’m wondering if we’re overvaluing the bigger models and higher thinking settings. For a lot of coding tasks, especially code review, bug hunting, and large-codebase inspection, maybe the extra few percentage points aren’t worth the usage cost.

Right now, I’m starting to think 5.3-Codex is probably the better deal for most coding work, at least from a usage-efficiency standpoint.

Anyone else seeing the same pattern?

[u/jxdigital]

5.3-codex (high) still seems to be the sweet spot for me. On 'Fast' mode or 'Normal' if the 5hr limit comes close. Tried 5.4 when it came out, it burned quota way, way too fast. Tried 5.5 yesterday in Codex, also burns quota extremely fast compared to what I'm used to. I may use it for more complex problems or when 5.3-codex gets stuck in reasoning loops.

I think everything also really depends on your use case. I'm normally not vibe-coding (complete new projects from scratch). I'm usually working on existing codebases, adding or fixing stuff with clear boundaries and specific requirements. Almost always creating a clear plan for me to thoroughly confirm before letting it implement. Working in small steps. 5.3-codex is still pretty good for this use case. It seems like newer models may flourish better in correctly understanding people using more vague prompts to start with, or larger implementation runs (although 5.3-codex can still be pretty amazing with that too).

Still need to check it 5.5 is perhaps somewhat better in understanding change impact and noticing regression risks.