Ali, of course. Ali was a pro and had been in the ring with the best, the strongest and the toughest heavyweights in history. Sure, Stevenson was highly-skilled and physically gifted, but he beat amateurs and fought under amateur rules where there's much emphasis on safety, so I guess, he wasn't used to "real" and tough fights against elite heavyweights like Sonny Liston, Joe Frazier, Ken Norton, George Foreman and Earnie Shavers, among others. Lastly, Stevenson, at most, was a refined version of Foreman, whom Ali outfoxed in Zaire. I see no reason why Ali would not outsmart an inexperienced Stevenson.

Stevenson was a great amateur boxer, not a great fighter.

Amateurs rarely peak that young, and its impossible to master the craft at a 12-15 round level fighting 3 rounds. It becomes its own sport.

Teofilo is one of the best ever at Amateur boxing, but he doesn't have even the whiff of a shot against a true great prizefighting champion. He never learned how to box pro.

Ali by what he wants any time after the 4th round

we will never know how good stevenson could have been if he had turned pro. having an age advantage would have helped him (stevenson would have been 26 in 1978), so i really don't know if he would have beaten an ageing ali.

Ali would of tore Stevenson up. Ali wins!!!