Sorry I think this misses the mark.
Because it's not the output but the process.
And sometimes the outcomes are not always discernable.
Codex and Claude are very different.
I use them for different things.
Their behaviour difference is obvious.
Of course it'd impossible for anyone to tell by looking at my code base 'how it was written'.
So the same person, was using similarly competitive tools, and showing that the output was hard to discern (indirectly the implication was also that implementation was fairly trivial in both of those). A better analogy would not be different process and widely different tools but for example two power drills. Sure, folks could still prefer one over the other, but that's a different claim that saying X is objectively better than Y when both are directly competing on very similar dimensions.
Assuming you meant Claude code: I'd love to learn more about "Codex and Claude are very different" because maybe I'm assuming just based on my use case where I use both of them interchangeably for the same thing (coding web and mobile apps)
The only way a reasonable comparison could be made, would be to compare completely automated results from either technology - that would be useful.
For example - creating a 'per-baked script' and running on both to see the output.
Codex and Claude are obviously very different, though it's hard to characterize how those differences might apply exactly to a given problem.
Two 'very different power saws' will ultimately build the same home.