The 270 is better. Having said that, I own a 6.5X55. I love the round but it is for handloaders. The only factory ammo worth firing is Hornady Light Magnum in either the 129 gr. or the 140 gr. My rifle loves the 140 gr. My hunting partner bought a Winchester Model 70 Featherweight in 6.5 and his rifle would not shoot worth a darn with the Hornady factory stuff. I worked him up a load using the Nosler 125 gr. Partition and his rifle is a tack driver.

The 270 is flatter shooting, packs more punch, and ammo is available nearly everywhere. This is why I say it is better. The 6.5X55 is just more fun.

Remember, any rifle in the hands of a rifleman is a good rifle.