My tho'ts are that the only advantage the 270 would have over the 280 for the same bullet weight and design would be a bit better bc.
The base of the 280 is 0.007" larger, which seems a small difference, but is actually quite a difference. With different expansion ratios, etc they are two quite different cartridges.
I've heard that a "well loaded" 280, especially an Ackley version, will rival the 7 mm Rem Mag. Be careful, cautious and conservative though.