I have 2 Kimber Montana's, 270WSM and 7mmWSM. You cant tell the difference between them unless your close enough to read the stamp on the barrel.
Same goes for the rounds they shoot. Pretty well have to hold them side by side or read head stamps.
I'm guessing an elk at any range wont know the difference either. Maybe an elk can feel the .007 difference?
The big help for the 7mm is bullet choice and BC. But for me the high BC bullets arent what I'd choose for elk anyhow, so......
If Noslers Long range accubond (150g .277, .625BC) is as advertised the 277 WSM will take a nice step forward.