Vitali wasn't a big puncher. He wore down his opposition, and they were mostly bums. Lewis had a better chin that Danny Williams, I'll give him that.
I would compare Marciano more to a Honey badger or a Wolverine then a Lynx. And they are known to kill all kinds of animals larger then themselves. Remember how Mercer busted up Lewis with his pressure now imagine Marciano doing that for a 15 round fight. Marciano could punch hard enough with both hands to seriously hurt a more big and more stationary type target. These smaller skilled like Charles, Walcott, Moore would probably be more trouble for him then some of the super heavies they are just going to get poleaxed and hard over and over. If Lewis had a great chin I would favor him, but against one of the greatest and hardest hitter of all time with both hands, his chin is to weak.
Lewis is better than Marciano both as a boxer and an athlete. People seem to have a real suspension of logic when discussing him in head to head matches. I think the Justin Fortune bout would be a far better blueprint than the Mercer bout.
With access to the sports science that they had in the 80s and 90s, Marciano would have been even more dangerous as well as physically fit. While I can't see Marciano winning a decision, I do see him giving Lewis hell.
He was as physically fit as humanly possible. What sports science would elongate those thalidomide baby arms?
This goees back to the size difference thing to most people. I don't buy it. If I did, who beats Valuev? He has 6" and 40 pounds over the super heavies in Lewis and the Klitschkos. He'd have how much size over the 210 pound 6'2 " guys.
The obvious difference is that Lewis is a much better athlete than Marciano--the same cannot be said of Valuev vs. the 210lbers. Lewis would beat Marciano at any sport.
Valuev had well over 40 lbs. on any great SHW. but he did not have the skill. STILL just with size, & not even punching partciularly hard, he went very far indeed.