You have to look at Leon's record for what it truly is. When he was clean and sober he was an Olympic and heavyweight world champion. When he wasn't clean and sober he was losing fights that he shouldn't have. All those losses after the DeLeon fight, he was a horrible alcoholic and was already suffering from CTE. I'm not make excuses for the guy. He was his own worst enemy but I can tell you that multiple boxing people I know or knew because most of them are dead now, swore that Leon at his best was better than Michael.
That could be true but part of being great is being consistent. Had Buster Douglas say been more consistent with his training and everything maybe he would be held in higher regard on all time surveys. Maybe if Oscar Bonavena didn’t like to drink so much he would have been champion? Who knows but have to go by what we got.
We can not get away from fact for much of Carneras career it is alleged he was mob controlled, so some of his record might not be as legit as might appear. But hey Carnera made the best of what he had, deficits and all. I would say Leon was better all round fighter, In the amateurs he was a Olympic gold medallist and World Championships medallist, he won World Heavyweight title in legit fight from a ATG, albeit losing it back in next fight.
It is a bit like asking whether an aardvark is better than an octopus, but Carnera definitely has the better record.
Ask yourself the question.. Could Primo beat over 15, even a Faded Ali.. Or could Leon beat Jack Sharkey, certainly not at his best??