I'd go with having a son...he could carry on the family name, and I wouldn't have to be worried sick about him once he hits puberty.
Gender doesn't matters for me. But i want a son, because i want to give everything to him which i never got. I want all his dreams to be fulfilled. I have seen worst days in life and have lost my childhood, so i want my son to do all the things which i was not able to do.
These days, it doesn't matter whether you have a boy or a girl. When you have kids, you will naturally worry about their well being. What you should worry the most, is how to bring them up.
IMO if you put preference, later days you may have problems with coping with the child with different gender than you've expected and wished for and thats not good for in parents' mind. I want both equally.
I want to have at least one girl and one boy. My wife and I haven't started having children yet because we want to enjoy each other and be able to take child-free vacations for a few more years yet.