I agree with everyone who says "the one you shoot best". I will add though, you have a lot of time to practice.

Ilike 308 if you like it and shoot it well. You can buy a lot of ammo and practice several times a week before your trip inexpensively. I like a little more weight in my bullets and that is just my personal preference.

You want to shoot a mag, go for it. He can't be too dead and it sure makes makes up for poor shot placement. I know you might waste some meat, but I doubt you will eat much of it any way after your first bite.