I have had 2 7mags for decades as well as a Rem custom shop 280 I got in the late 90s (and after nearly 20yrs I once again have a 7-08 in the safe). I say all that to say that if you held me down and FORCED me to choose only 1 from the 4 I would take a few mins to think about it because I love my SS stalker 7mag and the RCS 280 nearly equally. If I lived out west and mixed bags were annual I'd probably pick the big 7. BUT that 280 with a full throttle 160TTSX load is just as capable inside of a quarter mile on ANY game in the western Rockies!
My one WY mulie-sagegoat hunt was on a private ranch with alot of driving around and very little walking so I took my big Sako/Lazzeroni for farts n giggles. Had it been a more strenuous hunt without question my choice was going to be the 280!!!
Stick with premium or "enhanced" ammo for the 280 if you dont reload. The plain jane fodder for the 280 is pretty weak as originally the 280 was released in a semi-auto so the pressure was kept quite low!
The 280 SHINES with 120-150 grain prem. bullets at full throttle!!!
I cant think of a BETTER lope load than the 120 TTSX over a full tank in the 280! (and it will STILL seal the deal on any mulie)
HL