Why not the 7WSM? You are comparing two different capacity calibers. The 7STW will be the obvious choice if you are wanting to run a long ways to kill something, far out reaching the 300WSM. If you want something comparable to the 7STW in the .308 class bullet, then maybe look at the 300RUM. At this point then you compare recoil and how far you want to be able to kill something.
If you were comparing say the 7mmRem Mag, than I would go that route over the 300WSM just for the better class of bullet that can be pushed to long range. Had I known this when deciding on a rifle 2 years ago, I would have gone this route in stead of the 300WSM. I do like my WSM though, I just don't get the performance I was hoping for because of not having things I should have researched into.
If you go for the WSM, you need to decide which bullet you are going with. If it were a custom gun, go with a 1:11 twist instead of the 1:10. This will allow you to push bullets up to the 210grns and gain some velocity over the 1:10 twist. If you are going to go the route of 150 to 190 grain bullets than I would go with a 1:12 twist. I would not buy a shorter barrel than 26" if you want to maintain a higher velocity to attain greater range for larger game. Currently I am limited to about 800 yards for everything from whitetail down, just because I am not comfortable to shoot any further than that. Hope this helps.
Tank