On the one hand, Liston was a behemoth with huge size advantages compared to Marciano. On the other hand, styles make fights and Ali had a lot of respect for Marciano and his qualities as a pressure-fighter and puncher. This content is protected I would favor Ali against both of them. Anyway, do you favor one of them against prime Ali and if not who would be a tougher opponent for Ali or could have a better chance to pull off an upset?
Well we have seen Ali against Liston and his movement would always cause problems. I think Rocky has a better chance.
I will elaborate that Rocky had a great engine and was relentless and would not give in and could still bang near the end of a fight. He gets underated on here because of his size but that determination and engine mean he is a handfull and should not be underestimated.