My vote goes to the .280 Ai easier to source brass you can shoot standard .280 Remington ammo out of it to fire form the bass like any Ackley improved cartridges. You have bullet weights in .284 that range from 110 grain -190 grain . The .264 bullets go from 90 grains - 160 grains there isn't a huge difference between the two but you can get the .280 AI in a budget rifle like the savage axis ii