I have a little girl and I adore her. When I set out to look for a Yorkie I already had in mind that I ONLY wanted a little girl. She is a total flirt and whenever there is a male around she completely forgets that I am there! lol

She can also get moody and she is more playful and active than most little boys that I have met.
I do plan to get a little boy in the upcoming year because from what I have seen they tend to be more loyal than little girls and they seem to be more affectionate.
But I think the best advice (as some people have already said) is to let your baby pick you. Once you go to the breeder one will definitely pick you...and you'll fall in love...regardless of whether its a boy or a girl