RE: 300 Win Mag vs 300 WSM
The advantage for me is all in the gun, not the round, in the case of the A-Bolt it is 4 inches shorter and 13 oz's lighter than the full length magnum. If that doesn't make a difference to you then it will just be a toss up because there isn't a whole lot of difference in the ammo with less than 180 grain bullet.
Gordon