In their primes, not the 65 year old (or whatever the barber in Coming to America says) version of the Brown Bomber in there.
I'll go with Louis here. A 37 year old one gave peak Marciano a pretty good fight before falling to him. Marciano has the edge in one punch power, and chin was Louis being the greater puncher is the difference here. Louis by UD in a good fight and he might get dropped somewhere along the way. Marciano was a VERY durable fighter with under rated defensive skills. There's few heavyweights in history that would be able to knock him out.
I probably overrate Marciano but I think he still gives Louis hell in a prime for prime fight. Marciano was not easy to discourage and he'd hit Louis harder than Louis would hit him. Although of course it'd be a much, much more competitive fight.
Louis was dropped more times than Marciano by inferior fighters to Walcott. Jersey Joe was old in years but still a very cagey, dangerous fighter, who by the way was knocked out by Marciano anyway.
Apples and Oranges. I actually favor Louis, but Walcott was a very durable and skilled fighter. Not to a mention a very good puncher in his own right.
you do know Walcott pretty much beat Louis in 1947 right? and then Walcott put Louis to the canvas 6 months later and was beating him before being TKO'd.
Rocky Marciano had underrated boxing skills but Joe Louis is the better boxer. Marciano was a you can knock me down but out boxer. Louis would most lilely score at least one knockdown but I don't see a knock out. Marciano's best chance is by knockout in the late rounds. The most likly result is Louis by decision over 15 rounds in a closer than expected fight.
Louis, TKO 13. Louis would win the majority of the rounds, but Rocky would give him hell up until the stoppage. Probably score a couple of flash KD's.
even Joe Louis said it that he would had still lost vs Marciano in his prime, because Marciano was the kind of fighter that give him problem.