If you are referring to the 160gr Partition, it can only be driven to about 2800fps, and because it is a semi spitzer the B.C. is only .434. On the other hand, I can drive a bullet like the .264" 142gr Accubond LR to about the same velocity, and it has a B.C. of .719. So at 100 yards, the 270 has 125ftlbs more energy than the 6.5x55, but by 200 yards, the 6.5x55 has an energy advantage of about 20ftlbs. By 300 yards, the advantage for the 6.5x55 has grown to about 150ftlbs. As the range increases , the advantage for the 6.5x55 keeps increasing. If you look at sectional density, the 270 bullet is .298, compared to .291 for the 6.5x55, so it's pretty much equal. If you look at trajectory and wind drift, the 6.5x55 has an advantage at 100 yards, and that advantage increases significantly as the range increases. Recoil wise, the 6.5x55 produces slightly less recoil in an identical rifle.
Given those numbers, I don't see any advantage for the 160gr bullet out of the 270win, The numbers actually point to an advantage for the 6.5x55. Of course you are going to point out that the 6.5x55 has the advantage because of the much higher B.C. of the bullet, and you are correct, but the fact is that most 270win rifles come with a 1 in 10" twist rate, which will not stabilize a high B.C. 160gr .277" bullet. On the other hand, the 1 in 8" twist that many 6.5x55 rifles come with, have no problems stabilizing a high B.C. 142gr .264" bullet. So for the vast majority of factory rifles, with the standard rate of twist for each chambering , I see the 6.5x55 as having the advantage for a general use hunting cartridge.