The 30-06 will generate more energy because it shoots heavier bullets. The .270 shoots lighter bullets at a flatter trajectory. Also, the 30-06 is supposed to be the most versatile as far as hunting goes, but it also has the most recoil. My personal choice of the two, if I only got one, would be the 30-06 because you can buy a great variety of loads over the counter, and .30-06 is the most popular hunting cartridge, so I would expect a larger variety of loads for it and any place that sells ammo should have it. You can buy loads from the "accelerator" 55 grain sabot bullet for coyotes, up to 220 grains for elk and moose. For the price of the 100ATR, it's worth it, although it may not be your last hunting rifle.