Question/options first, justification below.
.270 Win with a 1-8" twist
.270 Sherman
Both of these let me stick with the do-all Jack O'Connor caliber.
6.5-284
6.5 Sherman
More velocity, more bullet options, maybe lose some elk capability?
.280 Ackley
Can share ammo with my dad.
Other?
My Savage .270 Win has become a project gun. 25% because I want a bit better long range capability than the factory 22" sporter barrel, 75% because I like to tinker for the sake of tinkering. So know that a lot of my motivation is "because I can". Hell, setbacks in "upgrading" this gun have forced me to borrow my dad's .280 for my first elk hunt in two weeks.