If elk is the biggest animal you are going to hunt the 270 WSM would be perfect if you like Mag rounds......bigger than elk the 300 WSM.
Having hunted both moose and elk extensively,I find moose much easier to kill.They may be larger,but they rarely go far once hit properly.On the other hand,I have seen many elk run a considerable distance after being properly lung shot.Any cartridge that I would use for elk,I wouldn't hesitate to use on moose.