Either one will work but I prefer the heavier bullets (150g) in the .270 Win for elk. A .30-06 with a good 165g would be my choice. May be what I use this fall, in fact. By "good bullet" I'm talking bonded or Partition at a minimum, TSX/MRX, Trophy Bonded, A-Frame or North Fork.
Since 1982, though, my primary elk rifle has been 7mm Rem Mag with 160g bullets. Its taken its share of coyotes, too, and more than a few prairie rats.