.270 Win. is a great all around big game hunting cartridge. I've used it exclusivley for years on many deer, a few pronghorn, one black bear, and many elk with excellent results. While the .308 Win. may offer slightly less recoil, ballistically the .270 Win. offers some advantages and disadvantages when compared to .308 win. For one, the 150 grain bullet of .277 bullet offers better sectional density and better penetration potential when compared to the 150 grain .308 bullet. Velocity for both cartridges in 150 grain are nearly the same, about 2850 ft/sec, give or take 30 ft/sec. Inside of 200 yrds the ballistics (velocity and energy) of both cartridges in 150 grain are very similar if not identical.
The advantage of the .308 win. is that you can go up to a heavier bullet to 200 grains. Trajectory and velocity drops off fast with heavier bullets Though the .308 shoots plenty flat with full velocity 150 grain and 165 grain bullets.
The advantages of the .270 WCF are that with 130 grain bullet you can load this round to 3140 ft/sec, and that is a flat shooting longer range round. In my experience the 130 grain bullet at full velocity offers enough energy out to 250 yards to fully penetrate and hit the vitals of a large bull elk. With 150 grain bullet you can duplicate the ballistics of the .308 Win or 30-06 springfield out to 200 yards and still have better sectional density with the .277 bullet.
fuzzybear pretty much said it straight!!