Why have "almost an ought-six" when you've already got the real thing? I've owned a few rifles in .270 Winchester, but only because way back in the wayback when, before Al Gore invented the Internet, I wanted a particular rifle (Ruger No.1 B, Interarms Whitworth Mauser) in .30-'06 but, not finding one locally, settled for the .270 Winchester version in stock. I've got nothing against the .270 Winchester and filled seven elk tags with it but it didn't do anything for me that a .30-'06 couldn't do.
I would agree that if you have a 300 WSM, having a .270 Winchester is kind of superfluous.
I don't understand this part, though:
I get that the .270 Winchester, .30-'06, and 300 WSM look different on ballistics tables, but they all do the same thing in the real world and a properly-placed shot with any of those three is going to kill any North American hooved game animal stone-cold dead.
I'd sell the Tikka .270 and not buy another Tikka, personally. I know they're all the rage on this forum, and personal taste is just that, but I'd rather get my A-Bolt II Medallion in .257 Roberts back, or have ANY A-Bolt II Medallion, than a Tikka.
I don't see what a Tikka is going to do that an A-Bolt II can't.