Re: 7mm WSM vs 7mm SAUM
The differences are subtle. Without modifying the mag box, and just generally speaking, Remington short actions fit the SAUM rounds somewhat more readily, and WSM's are probably a better fit in Winchester short actions (just because of COAL). Makes sense, doesn't it, considering which companies designed each round? Ballistically, the 7mm SAUM and WSM are fairly similar, with the WSM having slightly more case capacity. Either one is a fine round.
You're going to have to do a better job of defining "better". Maybe it's a pet peeve of mine, but "better", to me, is a concept that is vague and lacks focus, until it is clearly delineated. "Right tool for the right job", right? But, it's hard to choose the right tool until you define what the intended job is...