Competition is the difference, both punches could hurt a fighter. But Frazier's hook was showcased against bigger, younger fighters like Ali,Terrell, Mathis,Quarry, one great,rest very good all in or close to their primes. while Marciano's overhead right was showcased against J.Louis, A.Moore J.Walcock,E,Charles, all excellent or above average fighters at one time , but all were clearly past prime. But I'd rather take a chance walking down a street at night in Mogasdishu in the early nineties than being hit by either of them.