This bout is interesting both similar sizes Usyk is more skilled. However Ali is a bit faster is see Ali winning a UD. Who do you think would win?
If we are talking about 1967 Ali, he would have outboxed Usyk and won on points by a close decision if it was a 12 round fight. If we are talking about 15 rounds then it is possible that Usyk would have been stopped by knockout, although I am more inclined to think that Ali would have won by a clear unanimous decision.
It's a tricky one because when I consider these match ups I want to take into account other factors than just their respective skills. So much of a fight is physiological that aspects such as career experience play a big factor in the outcome. This being the case we have to factor in which Ali are we talking about? The lightning dancing machine of the 60s or the canny operator of the 70s who got by as much on ring generalship, showmanship and reputation as his skills. Overall Ali has so much more experience mastering a huge variety of styles and fighting when the heavyweight champ was one of the most famous men in the world. Usyk is a low key guy in a diminished sport which only appeals to hardcore fans. The level of fighting on a big occasion as a major celebrity and thriving in this arena is an underrated part of Ali's skill set. If we are plonking the two guys in a basement and holding the fight there then Usyk has the ability to win. But if we are holding this during any of Ali's peaks in front of thousands of his disciples Usyk will confront something he has never and will never have to face. We haven't really seen much of Usyk other than as a very talented boxer in a not very talented era. But I am not sure we have seen him face any of the challenges Ali had to overcome. Without that evidence I have to go with Ali.
As great as Usyk is, people are forgetting the speed difference. A 35 year old Usyk, quick as he is, is nowhere near as fast of hand or foot than a 25 year old Ali. Ali obviously never fought a southpaw like Usyk so i could see Usyk taking 5-6 rounds. But Ali's superior speed and amazing lead right hand (best weapon) vs a southpaw should give him 8 or 9 rounds on the scorecards (in a 15 rounder).