The two cartridges are virtually identical. .007" of bullet diameter is insignificant. The 280 having the shoulder pushed forward .05" is insignificant, only about .15cc more room for powder than the 270. 270 is nicer in factory loads because the selection is better, the price is lower, and the pressure and performance are higher. The 280 was designed to function in 1950's Remington autoloaders which didn't really like full pressure 270 loads, so Remington specified a 50,000 cup pressure limit for the 280, same as the old 30-06 Springfield.
If you handload, there are a few more bullet choices for the .280, (but .277 bullets span a pretty good range too) you can load your 280 single shot or bolt gun to .270 pressure if you want, and H&R gives you 4" more of barrel in the .280.