The really more important (competive?) measure, would be how many children one can responsibly bring into the world, via a proper family. Those who welcome their families to grow "traditionally very large," contribute so much more to the numbers of people that can then experience life, and to the human race, than those who merely pass on their genes to be "well-endowed." So size, as they like to claim, actually isn't quite everything. (But it helps, we would presume?)
What's the use of having an impressive "fire hose" or to be "hung like a horse," if it doesn't really do much to naturally grow families, so that all the more people may experience life? Yeah, it sounds like there's something to being "big" and more "filling," which may enhance sexual enjoyment, provided that love and all that is there too, but presumably, that only works to a point, although just how big it can be, before it becomes "too big," isn't very clear. Actually, the human body is rather adaptable and flexible, so such vague things are likely hard to define anyway.