I'd be happy with either, but my preference is definitely a girl. I've always got along better with girls than guys and I've noticed that too when interacting with kids.
Also I have girl names I like picked out. Boy names are hard for me to think of.
Might be interesting to know what the sex is of current kids. For example, I chose female because I already have two boys. We're not having more kids, but if we did I'd want a daughter.