It may not be necessary, but for heavier game and game that bites I like to carry the heaviest rifle I can shoot well. For me that would be my .338. In your case, the 308 NM would be just about perfect on Elk, bear, and African plains game IMHO. The 270 would work on them but to me it is best suited to deer sized game, since you have both to choose from.
Of course, we could get into a long discussion about bullets, BC's, drop and wind resistance, etc.... and make this a long winded conversation but since 99% of all game is shot within 250 yards, it really doesn't matter unless you address that specifically in your question....
Bob
