The version of Leon that beat Ali wins this. Just way way too busy and gets inside Micheal and lets those hands go. Nobody had to remind Leon to throw combos. Michael wants a guy on the outside playing the boxer game. That's where he's at his best. A pressure fighter is a different thing and sure changes his effectiveness and especially his workrate. He likes his posing and breathers and play the feint game. But a pressure guy is a whole different ballgame and the energy requirements. I also think the Coetzee blowout pretty much ruined him. A devastating loss. That's the caveat--it'd have to be the 78 version of Leon and not the guy showing up for the Ali rematch. After the Coetzee bout, Leon was down to journeyman status--with a name of course---but really on par with the Ledoux and Stan Ward and guy's on that level.
I think Michael Spinks was better then Leon. Leon when he beat Ali fought very hard and a good fight but I think if he was facing his brother Michael as a heavyweight that night he'd have eventually got caught and knocked out. I think Leon Spinks was a much better fighter then his career would lead you to believe. I think he could've held his own and won against some of the top fighters in the 80s when he was on top of his game which was at the time he beat a faded Ali. Still I think his brother was better and he beat Holmes twice at a time when he wasn't nearly as faded as Ali was at the point when Leon was able to beat him once.
Yeah, I'd make him a SLIGHT favorite over his little brother, at least that version. I just think overall, Michael Spinks was the better and more skilled fighter. Question is, how good was the version of Holmes that Michael beat? That same Holmes, 7 years later, beat Mercer and made prime Holyfield work for his money. Ten years later he went the distance with Oliver McCall, fresh off of a KO win of prime Lennox Lewis. I'd say the version of Holmes Michael beat was better than the Ali Leon beat. Let's put the Ali of the Leon fight 7 years into the future. Circa 1983, do you think Ali beats Tim Witherspoon or Pinklon Thomas and then takes Holmes the distance in a competitive fight, losing a decision? Half of that question was answered in real life.