This answer is easy: 70s Foreman easily beats 90s Foreman.

What did 90s Foreman actually do? He KO'd Michael Moorer with one punch, in a fight where he was losing every round. How many successful defenses did Moorer have as heavyweight champ? ZERO.

70s Foreman KO'd Joe Frazier and Ken Norton in a matter of minutes, and lost the title to the greatest heavyweight of all-time/