Ok, so I'll make a solid argument now. Sorry for the long while.
This is a pure AP match.
No, please... Don't say that. By saying that, you are dismissing so many things not only about Yujiro, but All Might as well. They are both extremely skilled combatants, and even with purely basic AP one has ways of "ignoring" durability to a degree. Joint locks, pressure points and internal organ damage are just a few of the ways that one can do so.
Now, playing the Devil's Advocate here, I'll say why I think Yujiro honestly wins this.
Not-so-much-AP Disadvantage: While it initially seems that Yujiro has a slight AP disadvantage, this is not completely true - See, the difference isn't that large. Noticeable? Certainly, and at the beginning of the fight Yujiro's certainly going to feel quite a bit the blows. But Yujiro has a way of equalizing, if not outright exceeding the AP/durability disadvantage. How so? Xiao Lee. With that technique, Kaioh Kaku - who is otherwise physically comparable to characters that are trashed by Yujiro, I think - can actually
hurt Yujiro and received
no damage from a full-power punch from Yujiro aside from a bloody nose. And Yujiro not only copied it from a glance, but also
mastered it. It is pretty much granted he can do the same. So, characters that he'd be unable to do any notable damage normally or characters that could one-shot him can't do either by using Xiao Lee. Even if we dismiss the Xiao Lee, Yujiro is stated to get stronger when he reveals his "Demon Back", further lowering the differences.
Skill: I'll be honest on this: Yujiro's just too darn skilled to All Might to overpower. Not only is he a
master of all martial arts in the world, but he can copy
and master any style by just
looking at someone using said style. That's his limit? Lol, no. Yujiro has sick analytical skills that won't allow any, ANY flaws from All Might's form or technique to escape from his sight.
He ofte determined every single fracture and wound one has received with nothing but a glance, to the absurd point of
discovering cancer cells that haven't even awoken yet and hidden physical frailties that are yet to happe, and that's what he does
without making any effort to do so. Not only is Yujiro several orders of magnitude more skilled - he actually can and will exploit any and all mistakes All Might commits in the fight.
Miscellaneous abilities: More of a support-kind of deal, but Yujiro's has plenty of ways about incapacitating All Might even if he is weaker than him in AP - and that's dismissing his skill and Xiao Lee! - by exploiting his other, more lethal techniques. Benda can cause inhuman and abnormal pain in those that it strikes to the point it can disable people just as effectively as a KO. Aiki can redirect one's entire force (So, All Might's superior AP can actually work
against him if Yujiro uses Aiki to make him hit himself or knock him to the ground). Joint locks in general work by that - unless the AP/dura difference is big enough - the more effort one makes, the more they will wreck the opponent's day. Pressure points are pressure points, I don't think I need to explain those. And finally, Yujiro's very aura can dissuade and subdue weaker men. I doubt it'd work against All Might, but it still should be noted. Like that time he
caused an earthquake by his bloodthirst.
