I think anything from .308 and up is adequate for moose, but I generally go with "bigger is better" as long as you're comfortable with it. I use a 375rum with 300gr a-frames.
The 300wsm is a great gun if you are only going own one rifle for Alaska -- for exactly the reasons stated above. I just purchased one but haven't got to the range with it yet. Of course, why would you only want one?
