I would go 280, got more punch and better SD and BC with bullets. Shoot 140gr. Or 160gr. NoslerAB- hard to beat and will get better velocity than the 308.
FE
While the 280 does have good ballistics, I will never, ever be without a 308. My primary hunting rifle is a 308 and I am in the process of building a heavy in it as well. It is so efficient and accurate that it is irreplaceable. Easy availability of surplus ammo also provides for an affordable route to a stockpile of ammunition.
Man is that a loaded( pardon the pun), question . I have a love affair with both. As a back up gun on a elk hunt, either one fit the bill. By the way, the rifle you picked is a good one. You could load either with 168's, and nothing would walk away from that. As a lover of both cartridges, you could almost flip a coin as far as performance, but you have to admit, the .280 is Sexy! Good brass is no problem with either. Have fun deciding. That's the fun part!