PUNCH POWE is a combinaion of speed and strength, not one without the other. Tyson was alot older when he fought Williams he had lost both. Look at RJJ, he has lost both speed and strength, do you think he could KO clinton Woods like he did a few years back? etc
I would say Foreman /Earnie Shavers Marciano are different to most fighters....they were cavemen with brute strength.
Pound for Pound, I'm assuming is the question. but if standing in a line to get hit with either a "Haymaker" or a Tyson Shot! I'd be in the David Haye line like a "Mug" (First in Line). Tyson had an incredible, Speed & Power Mix. (And his combo's were....)
The only reason Roy Jones would have had a problem with his strength in the last few years was because he had to come down in weight. Now that he has settled at his best weight there shouldn't be a problem with strength as it's one of the last things to go with age. Speed, whether it be hand speed, hand/eye co-ordination, agility, etc, is a completely different story as it's the first to go. This is why Roy is a shadow of himself these days because he relied on his reflexes and hand speed so much. It also affects his power as you mentioned but not his strength.
Take the speed away from Tyson's punches and it makes a significant difference....it's simple physics. Sure he was strong and launched himself when throwing those bombs but the speed at which they were thrown should not be underestimated.
Notice: Fighter A beats fighter B. A loses to C. Who will A invariably endorse when B fights C? Answer: B
if haye starts knocking his heavyweight opponents out like tyson used to then we may be able to make some comparisons but until then the argument is not even debatable!!!!
Just because he says so does not make it so. He could well be fibbing. There will not be a huge force difference between the hardest punches both men can throw, but you should never trust what a fighter says in these scenarios.