I've never hunted large bears or moose. That said, however, those who I know who have say that a .300WM is fine for moose, and they use premium 180 grain bullets, but prefer 200 premium bullets. For large bears, however, most have told me that they prefer cartridges with a bigger diameter, and suggest .338WM and also say that a .375H&H is not out of line.
Zachary