When I found that I had a stress cracked barrel in my .308, I chose to rechamber the new barrel in the 6.5 Creedmore, as opposed to the 6mm...primarily due to the fact that with a 1/8 twist, I could utilize a heavier bullet than with the 6mm...
While I'm currently in the process of building loads for a 123gr BTHP, I always have the option of going up to a heavier bullet if needed...For local shooting the 123gr will suffice nicely..
I do realize that the 6mm has a little higher following in popularity on the national benchrest circuit, but the 6.5 CM is a fairly new round to the shooting community and, to be honest, I really don't care what others use in the first place...