It's never a totally "logical" decision. For ONE GUN, and because you can always shoot 280 Rem ammo in the 280AI, I'd build a dream 280 rifle with the AI chamber, whether you shoot the AI ammo or not. But, except for the heaviest bullets that gives you 7mm Mag performance ina lighter, more pleasant to shoot and carry rifle than the .300 Mag., and the 6.5 just can't duplicate its potential in any sphere.
I have used a 6mm for many years and have taken lot of Deer and Antelope. My first rifle my Dad purchased for me. Never felt under gunned. Before I started Reloading I shot all my Deer with the 100 gr Core lock Never had a lost Deer. Today I reload and my new Rifle is going to be the 6mm Creedmoor. My niece shot her first Cow elk last year with her .243 80gr TTSX 200yards behind the shoulder and it went 50yards...............My first Black Bear was 211 yards dropped and never moved 95gr Berger .243 AI Lungs were like jello..............
Sorry I'm late to the party! That 280 Remington is a sorry excuse of a firearm. Just box it up and send it to me (I'll even pay for the shipping to expose of it for you). I promise I'll not charge you a dime more!
Sincerely, all 3 are great, love my 280 and my 300wm. Never owned the other, but have studied it hard. If it was me I'd keep all three of them and buy a few more! But if you insist, send me the 280!
I have shot my Dall Sheep at 535 yards and my 5x5 at 300 yards with my 6.5x284 both DRT. Would I like to have a 300WM sure but it still comes down to shot placement. My wife’s 6x6 was at 353 yards with a 3006 dead within 20 yards.