I use a 338 WM with 250 grain bullets and have never had a problem with elk or moose. Out of the 3 you mentioned, I'd say 30-06. Most hunters will tell you something 30 caliber although there are quite a few that use deer caliber guns with heavy bullets and do just fine. In the end, it depends on what you can afford, what you like and what type of hunting you're going to be doing.