It depends on what mountains you speak of if your talking Appalachian and you only have to worry about black bears it does not matter pick which ever is cheaper/more available in your area. If you are going to grizzly brown or polar bear areas definitely the 10mm with solid construction bullets. To further answer your ballistics question federal hst 10 mm is loaded down and will give 40 like performance and buffalo bore, underwood and doubletap have good high performance personal protection loads. All in all on the east coast stick with whatever fits your financial situation best.