Well lets cause some #### in the oldest running thread on CGN lol.
So what are the differences...
.277 vs .284 bullet diameter, minimal almost meaningless, marginally higher sectional density with 270 vs 280 with same bullet weights, so call that even.
Pressures....270 is a 65k psi cartridge, 280 is a 60k psi cartridge. Again, very little real world difference which equals almost identical velocity with same bullet weights, but advantage to the 270.
Twist rates....270 is usually 1/10 while 280 is 1/9.25. So that's pretty much the biggest difference....the 280 will be able to handle slightly longer bullets then the 270, whether that's lighter solids, or heavier lead spitzer, advantage goes to the 280.
BUT what really determines which one is THE BEST EVER GOAT.... popularity.
270 wins that one hands down.
Given the choice between a 270 or 280? I'd pick a 7mm Remington Mag....