I differ from the other two responders. They are both excellent rounds, but (though equally suitable for a wide range of big game hunting) ideal for slightly different categories of big game hunting. The .270 has a slightly longer practical range on medium game, whereas the .30-06 can take larger game more efficiently than the .270. In between those two extremes, they are very similiar in performance. So you have to decide if your hunting interests lean more towards larger game animals, such as moose, elk, grizzlies, or medium sized animals that are typically hunted at longer ranges, such as mountain sheep and pronghorns. If neither, i.e., you intend it only for deer and black bear, then both will serve equally well.