If you want something you can go anywhere with, you are definitely better off with a .270 than a .264 Mag... You'll be able to get .270 ammo just about anywhere. It's pretty much as common as finding .30-06 ammo. The .264 Win Mag is going to be a little harder to find if you happen to need some from a local mom & pop store because you dropped the box you brought in a puddle when you were unloading your truck...

The .264 also has recoil and noise penalties, without a lot of real, effective improvement over the .270's performance. Assuming you're not overly sensitive to recoil, I'd recommend the .270, .30-06, .308, or 7mm-08.

Action type isa personal preference issue. I'd rather have a bolt action than a pump. I've never seen a pump action rifle that was aesthetically pleasing, and you'll get better accuracy from a bolt gun.