In theory the WSM cartridge has less recoil. However, the WSM's are typically packaged in a slightly smaller, lighter rifle, negating the reduction in recoil. I have a Browning A-Bolt 270WSM, and like it. No doubt I would've been happy with the standard round as well.

Check ammo prices and availability in your area. Its hard to find WSM ammo in my area. You'll pay more for WSM ammo, and find less choices, though Federal is now chambering new rounds for the 270WSM.

Bottom line - find a rifle you like, and if it happens to be one or the other, it'll make no material difference.