We've only had a boy - he was lovely. I think girls are fun too but they can apparently be a bit whiffy when on heat - although some people don't notice anything and some hamster don't really have a whiff. They all have their own personalities really. There is a general thought that boys can be a bit more laid back (or even lazy!) and girls can be more active and entertaining, but it comes down to personality and genetics really. Probably the hamster will choose you
You will just see one, whether a boy or girl, that wants to come home with you. And if a girl is a bit whiffy occasionally there are ways of removing the whiff