It was my understanding that women prefered bigger than average sex toys which don't have feeling to them because they are static objects, requiring more effort from their user to pleasure, so a slightly bigger one has more chance, for less effort.
When concering vibrators and such, I figured they chose regular or smaller sized ones, to compensate for the vibrations and generate greater pleasure by having a non restricted space to operate in.
But you know what, I'm not a woman so I'm not even qualified to answer this question, lol. You should ignore this until you get some female responses. :)