Doubtful you'll see any difference, although the heavier bullets in the 300 may be a bit more useful on anything that bites back (like skeet said).
I've got a 7mag, and really doubt I'd ever trade it off on a 300WM. There are advantages to both, although the 300 requires a little more bullet weight for the same BC, which translates into more recoil. If you take dangerous stuff out of the equation, I'd opt for the big 7, but that's just me. It all boils down to personal preference.
gd