The 280 has a 1650 mAh Li-Ion battery, the 270 has a 1400mAh Ni-MH.
The 270 has 1/2.5/5 watt settings, the 280 only has 1/5.
The 270 comes with an alkaline (AAA) tray, AC/DC Chargers, and a cradle. The 280 only comes with the chargers and cradle, no alkaline tray.
I've used several 270's, and that's still my choice. Rock-solid reliability and very durable. The alkaline tray is a must-have in my eyes. I always have AA and AAA batteries with me, in my ditch bag. I don't have a 12v source, or 120VAC source with me... if I have to ditch, I want to be able to keep the radio going.