As a guy who has hunted Elk for 29 years in Colorado I would say that having two rifles of the same caliber zeroed in with the same ammo is a big plus. I can't tell you how many times a guy in our group has taken a hard fall and knocked is scope off in bad weather and heavy snow and had to shift to a backup rifle. Having a rifle that shoots the same cartridge makes remembering the ballistic table and drop at various yardages is a lot easier.

Having said that a new build in a different caliber is always fun and it's your money. The 270 will kill Elk and has by me and others in our camp but a heavier harder hitting cartridge brings benefits and can cut the tracking distance down. Where we hunt long shots are usually rare and most shots are 100 yards or less for Elk but for Mule Deer the shots can be out to 250 yards so you want a cartridge that dosen't have a trajectory like a rainbow.

Good luck with whatever you decide to do.