I think that all depends on where you want to take a look at the difference, and where the difference is. If the difference is only at the very top, you would only be able to see it on the drag strip or something similar. Then again, if there's only a 5-10 bhp difference, but the car has a nice fat mid to high range, that's definately noticeable on track or driving on some twisty mountain roads. This is why I love my bike, torque and bhp numbers are the same as those on japanese inline 4s, but my low and mid range is so thick, that they either rev the crap out of theirs or fall behind on corner exits.
All in all, big numbers will of course give everyone bragging rights, but in the real world, on the streets, flexible torque and usable power will always prevail, and make the owner happier.