Ali was a much more talented fighter, and I like to think he would win, because I far prefer his style, and also because Ali was a much more likeable person, with far better behavior, and AFAIK causing less misery in the world.
Tyson was very tough and heavy-hitting though. I think it depends on how successful Ali ended up in avoiding getting hit too badly in the first two rounds. He was great at not getting hit and wearing down his opponents. Tyson was great at hitting and hitting hard. So the number of actual hits would decide what happened, and would be a matter of fortune, luck, or specific movements, however you want to call it.
I read that Tyson himself said that he would not expect to be able to beat Ali in his prime.
One better breakdown than I can give on this question is here . I like his details, most of his category assessments, and his conclusion, which I like to think is right. I think it makes particular sense when looking at the types of fights each man lost to. Ali tended to survive and defeat opponents like Tyson – his losses were generally to other types of fighters. Tyson’s losses were to fighters who had strengths that Ali had (but who were not as good as Ali), and some of Tyson’s strengths (especially intimidation) and weaknesses (faltering when getting hit and not able to hit back, due to short reach and/or maneuver) play right into Ali’s strengths. So the article confirms what I suspected based on much less actual information.