I felt that Patterson deserved the decision when they fought in 1968. At that time I believe Jimmy Ellis was at his peak, having just won the WBA tournament. He was favored to win, so much so that Ring Magazine did not send a correspondent to cover the fight. Sports writers and reporters had already been calling on Patterson to retire. I have to believe that a prime Patterson would have been quicker and better. I would look for prime Patterson to win by a TKO in the later rounds. (Incidentally, the 1968 bout between Patterson and Ellis was the only time Floyd went the full 15 rounds.)
Given that some felt an aging Floyd deserved the decision in their actual match, I think he should be heavily favored prime for prime
Based on their actual fight ,when Floyd was past prime I would have to pick him to beat Ellis,but Ellis always had a fat dangerous right hand which could turn the trick.