I'm not taking one side or the other on simple PSI but just the momentum of a taller, longer, heavier fighter would lead one to believe he could hit harder. That said Tyson's power came as much from speed and timing as anything else.

I guess you could look at MLB pitchers and argue about who throws the hardest and both guys regardless of size could throw the same speed for example the 300+ pound CC Sabbathia and the pint sized Tim Lincicum probably throw the same speed. All a matter of mechanics.