There are PLENTY of highly reasonable explanations for the appeal of smaller women OTHER THAN the subconscious creepy explanation put forward by El C. Are we to believe they are all just so much window dressing or rationalizations to cover up the real basis for our impulses or a form of denial? Perhaps, but they all seem very credible to me. I will second most of the explanations provided by T&V and will add some of my own:
1) For Cowgirl or Reverse Cowgirl (and "spinning" between those 2 positions), smaller women are much better. They won't crush you with their clumsiness. They're light and energetic enough to sustain their bounce for much longer than larger women. And, if they do tire out, they are light enough for you to grab on to their asscheeks or hips and help them sustain it even longer with some "spinner curls". BTW, I should add that I like these positions because they're an opportunity for the gal to do more of the work, but for those who say the preference for smaller women is all about an issue of dominance and control, it is interesting that these positions are NOT normally considered traditional "control freak" positions.
2) Like T&V, I don't like the sight of belly fat and butt cottage cheese. I'll definitely still go with girl of medium height (or even taller) AS LONG AS they're still slim. Unfortunately, while taller women can be devoid of excess fat, when they are they often seem like skinnier stick figures compared to the ones who are small in both height and girth. OTOH, short chubby girls don't do much for me either. Shorter, smaller, slimmer women are the body types most likely to be devoid of that extra flesh and still look good. At least to me, YMMV.
3) Smaller women also tend to have smaller and thus tighter pussies. More medium sized women are not too big a problem for me personally, because I already have such a mammoth tool to work with

, but an even tighter fit usually doesn't hurt (though I'll admit I have run into 1-2 tiny girls who were actually TOO tight). BTW, I liked the image painted by Pac55 about a large (or in his case medium sized

) dick going into a tiny ass making it seem even larger.
4) Not sure if T&V's next claim is true but I'll go with it. Smaller women DO seem to be more likely to be high energy instead of bed slugs.
5) Unlike JB, MOST guys prefer women that are SMALLER than themselves. I suppose you psychologist types would say that is because that makes us feel larger ourselves. I can live with that. If you're fairly big and tall as I am, it doesn't really take a tiny girl to do that. For guys like me, a more medium sized girl should SUFFICE, but smaller women still provide even more of that feeling of size and, yes, dominance or control. And I can live with that too.