Greater bullet selection with higher BC bullets available in .284 over .277. More case capacity in the AI version, guessing around 100-150 fps faster if you handload.
If you handload, I would easily pick the 280 AI over the 270. My 280AI is shooting the 145 hammers at 3175 with RL26 and I never reached pressure. The rifle liked that load.
I have a .270 that is shooting the 140 bergers at 3040 with h4831sc, I have pushed it to around 3200 with 145 eldx and rl26 but that was max load.
@MuleyFever No plans to shoot suppressed, but the brake I have adds 2”. I’ve read a multitude of opinions on 280AI barrel length. Do you recommend 24” or longer?
Don’t know anything about the 280AI. But have two Rem 700 280‘s, both with 24” barrels. Had a 280 A-bolt with a 22” barrel. Liked all 3 equally well. Shoot 3 Tikka’s in 270 with just over 22“ barrels. Like them all too.
Between the two you mention, if I wanted max LR performance, I’d probably go 280AI and 24”. Otherwise probably 270 for ease of ammo, but I’d order it with a faster twist barrel, just in case I want to shoot some of the newer .277 heavier weight bullets a bit further.
Barrel length really means nothing without putting a max range into play.
For instance, people can say you need a 24" barrel to get the most from a cartridge. This may be true but do you need the most from the cartridge? If your hunting deer in the wooded Midwest and dont expect to shoot over 200 yards you will have no issues with cutting a 300wsm to 16".
If you want a 280ai and only plan to shoot to 400 yards cut it short, or buy a 7mm-08. If you have dreams of hunting elk to 800 yards you may want a 24"+ barrel.
280ai is SAMMI now, so ammo if you don't reload is available for both. I'd take it over the 270 in any barrel length for it's bullet selection- especially if you want to shoot if further out (higher BC) using a "dailer".
Really it's your choice. I know a lot of people out there are saying more bullets choices for this cartridge or that one, but honestly, if you reload or not, most of the time one will find the ammo/ bullet combination that is the most accurate and stick to that. I reload and admit that it's fun trying different powder and bullet combinations, but honestly, I have specific loads for all the different cartridges I shoot, because I get the best speed, accuracy and performance for what I'm looking for and don't change it. Either cartridge you're looking at will suit you just fine, 270 will be easier to find ammo and or brass for though.