There is no advantage of buying a .280 Remington - also known as a 7 mm Remington Express over buying a 270 Winchester.

They both use the exact same shell, they both hold about the same amount of power. The only difference between the two is that the bullet diameter of the .270 Winchester is .277 and the 280 Remington is .284

If you can even see .007 thousandths difference between the two bullets - it would be a miracle. You can get both rounds with the exact same bullet construction - and the exact same bullet weights in hand loads.

The bullet sectional density would be better in theory in the 270 due to the fact that the bullet would be longer and narrower in the .270 compared to the 280. Even that would be splitting hairs.

A normal human hair is about .003 thick.