The big thing with the SAUM seems to be that it's got a longer neck, and fits in a short action better than the WSM.
If you check out sniperhide, there's a couple guys that built some majorly badazz 7SAUMs and are running 180 Bergs at like 3015 (albeit a 28 inch tube ;)). I think the SAUM is a great little cartridge, I'd like to slum one soon.
That being said, I don't think you can go wrong with the tried and trued 7 Remington! But you'll be different with a SAUM
