I'd want something I could get ammo for. If you're not in a unit where you can basically choose what you use and which will order whatever you wish, how certain can you be that you are going to find non-issue ammo in BFE?
The smart choice, in my opinion, is to carry the issue sidearm with issue ammunition and sleep well at night knowing you won't have to worry about not being able to practice because you can't find ammo.
The smart choice, in my opinion, is to carry the issue sidearm with issue ammunition and sleep well at night knowing you won't have to worry about not being able to practice because you can't find ammo.