If you are starting out with your gun collection there is really no reason to buy both.

The differance in performance is that the 280 will fire a 160 grain bullet at about the same speed as the 7mm-08 will fire a 140 grain bullet. Or about 200 fps faster with the same weight bullets.

With the same bullets there will only be about a 4 inch differance in trajectory at 400 yards.

The big advantage the 280 has is that there is factory loaded (big four) ammo available with heavier than 140 grain bullets should you want to hunt bigger than deer size game.