I have a 6.5CM, and I quite like it, but it's a target gun.
The fellows at the LGS (Local Gun Shop) passed on many reports of deer getting hit with the Creedmoor and walking away.
I'm a big fan of the 6.5x55 Swede, and it's probably killed more moose than any other gun, but I'm not sure that there's really much difference that an animal will notice.
So, take that for what it's worth...
Welcome to the world of firearms where things don't always make sense, and people can have very firm convictions based on nothing more than 'I have one, so it must be the best ever.'