A followup question would be:
Why do people get so defensive, and take it as a slight to the great Marciano, when it is said that he would lose to Ali?
As was mentioned before, Ali outweighed Marciano by almost 40 pounds, had a 4-inch advantage in height, and far outreached Rocky. The physical differences alone are significant. Add to that the difference in speed, which Ali clearly had over Rocky... and it's not a reach to say Ali would beat him. Don't forget Ali had a pretty good chin, also.
It's not a knock on Marciano... it's just two different eras of boxing. By the same token, would Ali sweep through the Tysons, the Lewises, and the Klitschkos? Most likely not. Different eras... different sizes of heavyweights.
Picking Ali over Marciano is neither a slight on Marciano, nor an enshrinement of Ali.
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