Which ever one has the testes will be the hard headed one. Doh! that would be both of them huh? You get my point, males is hard headed. In fact my last (last that I will ever own) Brittany was a big male. Whoa what a hard head.
Males are fine if you neuter them at six months old. This stops a lot of the strong male behavior from developing.
My advice is get the strongest acting female from the litter.
Good luck Bro.