In my head here lately I've been contemplating switching out my 9mm XD Sub compact for something with maybe a bit more power, like .40 S&W. But really would there be much benefit? The other thing partially motivating this is ammo availability...I don't seem to have too much trouble find .40 anywhere vs 9. I'm just not very up on handgun calibers and am looking for some opinions, as this would more then likely be a carry gun as well.