The .270 is basically the 25-06, 30-06, and 7mm Rem mag in one package.
If you own a .270 you don't 'need' any of those other cartridges listed. With light bullets, it's an ultra flat shooter perfect for varmints and small game. With heavy bullets, is as every bit as powerful as the 30-06 and capable of harvesting all the same game but with certain bullets, potentially has better long range performance. With hand loads and a 24'' barrel. The .270 can be loaded to near 7mm rem mag level.
A 150 grain bullet with a G1 BC of .625 being fired at a MV of ~3000fps, is nothing to turn your nose up at. With that load you should be able to have 1000ft/lbs of energy past 800 yards.
IMO the .277 caliber is underrated, but it's not going anywhere.
Heck, it's almost as good as a 30-06!
I'd argue the .270 is 'better' than the 30-06
I consider .270 to be 'better' on paper than .30-06 because it will shoot bullets with comparable sectional densities faster and flatter than the 06 with equal if not better BC's. And depending on the load, will shoot bullets of equal weight (and higher SD's) almost as fast, if not as fast as the 06'
150 grain .30-06
SD .226
BC ~.435
Velocity ~2910 fps
150 grain .270 win
SD .279
BC ~up to .625
Velocity ~2830-3000 fps
If we compare bullet with comparable SD's
120 grain .270 win
SD .223
BC ~up to .460 (
http://www.midwayusa.com/product/479...ProductFinding)
Velocity- easily in excess of 3200fps.
The way I see it the .270 is measurably better on paper. Game wont likely know the difference, when they're hit in the same spot. (but IMO .270 is easier to shoot making accurate hits easier) but the .308 cal still has more choices for projectiles, much wider projectile weight selection for factory ammo, and longer barrel life.