I have hunted the prairies for 49 years for mule deer. Only once in all of those years did I find myself taking a shot over 300 yards.
Kinda hard to argue with that. The reality is under 300 yds most rounds are so close its hair splitten really. The 7mm mag is a more versatile round in that its also suited to elk and moose but likely won't do anything to a deer sized animal that a .257 WBY couldn't.