Neither imo... If anyone, I would vote Liston. He has a little 'Jirov' going on. Ali fans need him to be good, to help Ali's legacy.. Just like Toney fans (to an even greater extent) has elevated a mediocre fighter to greatness... because this is needed to boost the idea of Toney's career.
They were all great fighters.. But if i should give a vote: Foreman.. Frazier, Norton and Moorer were great wins, then he has a some good/decent wins (Savarese, Grimsley, Schulz, Roman etc).. I know that the destructions of Frazier and Norton were exceptional, but i just don't think that he deserves to be ranked top 5 on the ATG HW lists. I also think that he is a bit overrated in H2H matchups..
Alot of people will say Tyson. Its a tough choice, I would say Foreman to an extent. Valuev beats them all
They would both be competetive in any era, and either of them could win the lineal championship.. imo...