i'd opt for the .50 You can get 50cal bullets in the .45cal weights so, theres really not that much of a difference. Some states like colorado require that you use a .50 + for elk and moose. If you want a .45, i have a website where you could get a winchester apex for $200 give or take.

This place has the black/blue apex for $199, But for $60 you could get stainless steel and thats the way i would go. Its nice not having to screw around with the idea of rust being in the bore.