I'm with the others on this one as well. Though either, with well placed shots, will get the job done. You certainly aren't leaving yourself much room for error. If you already hunt elk you well know how tough they can be.
IMO, there just isn't enough gain to make it worth only stepping up to the 7rem mag. Like someone already said, find yourself a nice used 338win mag. Put a good quality brake on it and it will feel like your 270 or less.
kc, you'll enjoy shooting that big Accumark. I had one just like you're getting and with the accubrake it wasn't bad to shoot. Never shot it without the brake as I'm sure that would have been another story.