The 270 WSM can have very similar ballistics to the upper end 6.5's but where it shines is you can take it past what a 6.5 is capable of and even past what the 7mm's of similar size will do just because of the upper class of BC bullets available to the 270. In hunting the 270 can far outclass the 6.5 due to the availability of 165+gr bullets, if your twisted correctly to utilize them. Throat life will be a little better with the 270 WSM but it's not going to double or anything like that.
My dad shoots a 6.5 Sherman using a 140 Berger at 3150 and I shoot a 270 WSM using a 165 Matrix idling at 3053fps and there is just no comparison when the bullets land at long range, he can wail away at a little plate we shoot and I hit it once and it flips the plate and craters it. I also have a range advantage, I don't think twice about wackn an elk at ranges the 6.5 is maxing out.
With the 170 Berger coming, and if people start twisting their 270 up to a 8.5-9 twist there just is not advantage to a 6.5 or even a med sized 7mms, one 270 covers it all better