RE: Caribou cartridge
It's all been covered for you here, get the .308.
Just to let you know, another caliber that would be good for caribou would be the 7mm-08. It's ballistics are slightly superior to the .308, but only slightly, they are pretty much the same in performance,IMO.
I'm not suggesting you get a 7mm-08, I'm just saying it for future reference.