Oh gosh! Tough decision! I would prefer a yorkie over a maltese, but I would prefer a boy over a girl! I have 2 boys and my mom has 2 girls... her girls are a lot more independant and stubborn where my boys are way more laid back and cuddly! Her girls won't lay with you for more than 2 mins, whereas my boys will get comfy and not move for hours if you stay there!
Im sure it is all about the individual dog's personality but I just love the boys!