Um, actually, while most xy individuals are male and most xx individuals are female, it does not always work that way. Fetal development depend on hormones in the womb. Typically the hormone pattern follows what chromosomal information would indicate, but that is not always the case.
Interesting to note: ALL human fetuses begin as female and may deferentiate to male during development.
My personal oppinion is that gender is irrelevant except for medical reasons (i.e. testicles vs. uterus) and personal preferences regarding personal romantic relationships (for instance, I would not date a female to male trans because I like dick, and most available surgeries will not give them working dicks).
People get hung up on labels because we accept gender sterotypes: that certain fashion and behavioral traits belong to a certain gender.