In my experience the standard .270 Winchester is a great killer on a wide variety of plains game.
Apparently this is also the experience of a lot of hunters in Africa, especially South Africa, because it is quite popular there.
I have considerable experience with the .270 myself, as well as the .280 Remington and .280 AI. They are all pretty much peas in a pod. You can make arguments for the .280's with paper ballistics, but game all dies about the same when you hit them right with any of the three.
