I realize there's not much ballistic separation between the two but I'm planning a long range build and from what I've seen barrel life and brass quality seem to favor the 7RSAUM.
What are you really looking for? Is your WSM shot out? I don't think see much improvement to be made. Is this a Christmas present to your gunsmith?
What better quality brass are you getting for the RSAUM? All of my WSM brass says Norma on the head. Even my 7mmWSM's.