I’m going to make a public service announcement out of this.
You all think that we lie when we say that small cock will get the job done, or that “it’s not the size but how you use it.” You think that’s a well-intentioned lie, don’t you? The truth is that the sensation is simply different. A smaller dick will poke at places that a big cock will cheerfully pass. The pleasure is different. Where a big cock will challenge her and give her pleasurable pain, which a girl may well get addicted to, a smaller toolkit will give her tingles through the g-spot that a big dig will just ignore.
Also, there is such a thing as too big, or, rather, too long. If he can’t get deep enough to rub the clit with his pelvic bone, that’s not excellent. It is also possible for a guy to be so big that he cannot keep fully erect due to the amount of blood needed to “inflate” the penis, and that frankly makes his cock feel very ordinary, as he’ll be soft where she’ll squeeze. A heavily armed guy may also be too cautious with his toolkit to actually use it for good, so to speak, so… You know, it might be just psychological – the amount of times when one gets across weaponry of that size is not often enough to make definite conclusions. 
So, sorry, you big guys. The small guys have decided that her pleasure, rather than your ego, is more important and reincarnated with a smaller kit; having said that, I still slightly prefer the sizable tool, mostly for the visuals and the love of pain, rather than the actual, objective function.