throughout my lifetime i have owned & fostered many & find it about equal.
I think it just depends on how the dog is raised & cared for. Right now I have one of each & they are both very sweet & loving.

As far as preference, I ussually just look for one i like regardless of the sex, although occassionally ill get in a moood where I really want a prefered sex but again if i find a good dog that will change my mind. There is one exception though, like right now IF I were to get another dog it would probably be a male ONLY because my female does not ussually get along w/ other female dogs even with socialization & training so on & so forth. (long story but she came from a really bad home so he probably has an excuse somewhere in her goofed up mind lol)