O.K John..I will take the bait..

First of all, I don't think it is "at the moment" as its been growing and growing for the past 8 years or more...they were using this cartridge in all the range guns when I went to a long distance shooting school 2 1/2 yrs ago...claiming its virtues at that time of excellent accuracy and long range performance...yes, compared to the 6.5x55 that is a relatively short time, however with the advent of LRPR competitions increasing by leaps and bounds, the 6.5 Creedmoor will only grow in popularity as the years pass..or, some are actually now using the 6 Creedmoor ....

Both the 6.5 Creedmoor and 6.5 x55 are great cartridges. The 6.5x55 outperforms the Creedmoor when loaded to higher pressures. 6.5x55 load data is very mild because of old mauser type actions that can't handle the pressure a modern bolt action can, but in a modern bolt action the Swede can be loaded a lot hotter and surpass the 6.5CM or 260. Only downside to the 6.5x55 is, I have been told, it needs a long action to bring out its full potential, and if you go with a long action, there are better rounds available (6.5-284 and 6.5-06 both greatly outperform the Swede). With all this in mind, I suggest going with the 6.5CM since it is a true short action round and performs very well out to 1000yds.

I personally don't know enough nor have I ever used a 6.5x55..and frankly probably never will..to me it doesn't make sense at this point with so many manufacturers now chambering for the Creedmoor,feel like I would be hamstringing myself in doing so...at least when I comes to the Long Range Precision Rifle scenarios...for hunting, different story and actually been eyeing a Sako in 6.5x55 ..really nice rifle...but, will have to wait till I get back from Turkey..

Think this gives good info on what is real or perceived to be the "greatness" of the 6.5 Creedmoor

http://www.range365.com/65-creedmoor-long-range-king