I really don't know what to tell you. I shot an '06 as my only rifle for the first 20 or so years that I hunted big game. Since then I have messed around with a lot of different stuff, but have shot .270s, .280s (both the Remington and AI versions) and (occasionally) my old '06 more than anything else. I'll be damned if I can tell any difference in "killing power". For me, the .270, in rifles that fit me and shoot accurately, is just what works best for me.
I will readily admit that I don't shoot animals out to 600 yards. My longest kills, mostly on pronghorns, have been not much over 300 yards. Most of the Coues whitetails that I have shot (critters that supposedly require sniper rifles and scopes) were taken at less than 100 yards--same with desert mule deer. If I had never bought anything other than the old pre-64 .30-06 Model 70 that still resides in my safe, I think that my results would have been about the same--but I wouldn't have had as much fun as I have had trying other things.
