Virtually the same. I think the WM is a better choice if: you prefer a larger (not by much) selection of factory ammo, if you reload (which may be contradictory, but it's easier to seat longer bullets) like a little heavier rifle, a little cheaper factory ammo, want a little more top end.
The WSM is a better choice if you want something a little lighter, a little less recoil, like short actions.
For all practical intents they are equal. The WM may be a touch more accurate. The critters will not know and they are both FABULOUS rounds!! The coin flip is a no lose proposition. My $.02 USD
