Using 140 gr bullets in the 270win and the 280 rem there's not a nickel's worth of difference. They are pretty much identical in ballistics. If your a fan of heavier bullets the edge goes to the 280 rem. If your a fan of lighter bullets and trajectory then 270 win has the edge. Like RR said past 500yards the heavier 280 Rem bullets hold a advantage with their higher BC. I'm a 270 fan but I would not hesitate to add the 280 rem into my collection for a medium range target rifle using 162 gr bullets.
Fritz your right in medium to short range hunting situations the shorter barrels work great. I've taken elk up to 365 yards with a 20" 270win and seen another family member take a bull elk at 470 yards with the same rifle. Both elk required one shot. In the tree's they are handier for sure. I shoot a lot of open country and I don't mind getting that 35-40 fps for every inch of barrel added on. Depending on caliber barrel length can sure add to less guess work with trajectory in the field at the 400 yard plus range. Even in run of the mill local shooting matches trajectory sure does give me the speed advantage when shooting steel matches where it comes down to hits vs. time. I love simplicity give me a flat shooting accurate rifle with a simple scope and before most can get the animal ranged it's on the ground. That's just how I was taught old school on trajectory. Speed kills but accuracy is king. Combine them both and that's dangerous.