It all depends on the little girls personality if she is well rounded if everything apart from the dominance issues ie house trained ,well socialised etc well you have an instant little girl but if it's a puppy you want go for the boy or wait for a baby girl.
When I got Alfie I wanted a girl so badly ,I even had some things in pink things!!! But when I went to see the puppies Alfie just melted my heart and I was sold hook line and sinker.....

So if you are going up anyway let the doggie chose you but be careful, dont take any of them if you are not ready. As the little girl seems to have been run around a lot and it would not be fair to take her if you dont instantly want her, and the little boy deserves to be loved and kept forever.