Well, from what I hear from male friends who have asked me about this question - being that I seem to be an overall, (trusted advice giver) to these friends, because I haven't a carnal nor romantic interest in them, I'm asked IF I know what other women believe as to this topic. My answer seems always to be the same, as many women as there are, there is variety as to what they like, or prefer.
And as far as a man's confidence depends upon, I suppose that size would enter or influence either lack of self esteem, or how confident they already ARE (not so much size) as to perform as good lovers.
I truly think it is performance, and true give and take between lovers which makes the difference. No size. For there is nothing so disregarding as a well endowed man who is unaware of his partner's presence, ALSO, while love making.