Weatherproofing of the rifle.
The .300 Win Mag is fine for elk, and the .270 (IMHO) is suitable for anything outside Africa (and Blue Whales).
As the folks deduced, I WAS speaking of recoil. I am not a wimp. I actually have bits of paper that say that. And I have been a rifle shooter for several....decades. BUT-
I have a Remington 600 in .308. Looks like it was designed for George Jetson. Weighs 6 lbs, even. It puts marks on me. Really. Serious marks. A 6lb .300 Win Mag would not only knock your fillings out, but we are talking about detached retinas. Having the mark of the scope on your brow sutured. Developing the mother of all flinches.
And after stalking an elk for hours, to miss it because of a flinch is just unprintable here.