Michael for sure was the better of the two but Leon was a bad dude as an amauter and early on in his pro career. Leon gets dissed a lot for how his pro career went south fairly early on due to his partying but he won a gold medal in 76 against some pretty good Soviet and Cuban fighters plus Micahel Dokes in the Olympic trials. Unfortunately for him he had a short prime. He had the heart of a lion and is paying the price for it these days.
I've heard stories of how Leon used to whip Michael when they were kids. 50/50 imo. Little brother syndrome is real.