Shots at caribou can be longish, so I would pick the 300 Win Mag hands down. All will do the job of course in perfect situations, but since hunting is unpredictable, carry the biggest tool for the job. Use a 180gr. Fail Safe, or comparable bullet and you will not be disappointed. The Fail Safe is the deepest penetrating bullet on the market, and with moose penetration is critical. Good luck!