Dirrell's performance was a masterpiece, Hopkins overall has a strong body of work but not one single performance that rates as high as Dirrell's. I take nothing away from Hopkins though, he is a great actor.
Dirrell was the better actor, because some people think it was real!!! Everyone could see Hopkins was faking it.
Hopkins acting has consistency, from Robert Allen to Calzaghe to RJJ many more performances. But Dirrell did the single best acting. H2H Dirrell is the better actor.
All of Hopkins' acting is against post-prime/shot fighters. Dirrell's acting against a prime hungry opponent should get more credit.
That said, Hopkins longevity means that I now have him Top 20 ATG on my personal list. Somewhere around Newman, Spacey and Day Lewis.
The answer is Arthur Abraham. Look at the post fight interview. He swears up and down that it was a legal punch and a legit knockout(which means he had to have thought Dirrell was really hurt). Then after he sees the replay and sees that Dirrell was clearly down, he changes his tune and claims Dirrell is not a boxer but a good actor. Although he blatantly contradicts himself, Abraham sounded convincing both times.
That aint putting on a act the only thing close enough that could be considered AA's acting was when he had made everyone think that he is a nice guy that is always smiling, then hospitilizes people
If Dirrell doesn't get the nod from the Academy it'll be the biggest travesty since Peter O'Toole didn't win Best Actor in '62.