SOMEONE MADE THIS! YEEEES! YEEEES!
Anywho, gonna vote X with Mid Difficulty.
Copy X should have the AP/Dura advantage (via MMZ > MMX scaling). But it's not meaningful given it's not that big of a gap and Mega Man X has experience fighting stronger people anyway (i.e. Sigma, Awakened Zero, Lumine, etc). And... that's the only advantage Copy X has, really.
Mega Man X holds every other advantage like MUUUUUUUUUCH wider versatility and variety of armors which allow for screen nukes, having access to AP & speed amping chips, etc. He should also come close to skill stomping Copy X given that Mega Man X = Zero consistently (who is an absolute monster on his own given when he was in an animalistic mental state he out skilled multiple Reploids at the same time who should be all be > to Rock in skill -via being based off of X's design- who is already very skilled on his own).
Also, I forgot to mention Copy X should have all of Mega Man X's resistances due to the former being based off of the latter's DNA. Guess that'll need to be added in the future.
Anyway, voting Mega Man X for my reasons.