Hard to say. But being that Ali faced Liston, Foreman and Shavers his may be more proven. How many times was Foreman actually hurt in his career though? The Lyle fight definitely. But where else. Not stunned like the Cooney bout but actually hurt and in trouble. Ali and Young got him with exhaustion
Foreman early in the fight and Ali late in the fight cause obvious stamina motives. You have to take in cosideration also that foreman was much easier to hit than Ali. I never could imagine cooper hurting foreman even landing clean with his best hook in the chin
If you put both them in the first round and the same puncher landed with the same force in their chins and i say that Foreman takes it a little better.however Ali had a great capacity to recover
The man who collapsed like a house of cards from a Cruiserweight left hook did not have the same resistance as the man who took bombs from Shavers. That Ali had more beard than Foreman.