Your not going to notice the difference. Pick the one with the best brass availability which is the old work horse the 7mm RM. That way your not pulling your hair out or scouring the internet for 7mm wsm brass.
Would this be used for hunting or just range work, or both?
I have owned both of them. The wsm was in an xbolt with a 23" barrel and was a pleasure to haul around the mountain. My 7mm Rem was a M700 and it had a 26" barrel and was a little heavier.