If I were to buy a rifle in which I could choose one of the two shells named , I would take the 7-08 because I live in Wyoming where my common game is elk and deer are in 2nd place for me. Not that the 6.5 lacks anything there, but I can use 160 and 175 Grain 7MM Bullets that I used years ago in my old 7X57 Mauser at the same speeds from the 7-08, and I know how well they work. There is nothing new to learn for me with this combination.
I hope to learn about the effects of the 160 gr RN Hornady 6.5MM bullet this season, as I am going to hunt with my 6.5X54 Mannlicher, but it will be my 1st elk kill with a 26 caliber rifle if I am successful. If that bullet, leaving at 2250 FPS is good enough I bet it's good enough leaving at 2400 or 2500 too from the Creedmore (or the 260 Rem)
But the only 160 grain bullet I know of that's available today in 6.5MM is the Hornady. Sierra quit making them, and Hornady don't make a lot of them. So 160s in 6,5MM are rare.
160 and 175 Gr 7MM are common and very good on elk.
Now if some reason I were a Wyoming hunter and didn't want to hunt elk I would choose the 260 Rem or maybe the CM, because both would be super good for antelope, another animal we have in abundance.
But to be 100% honest, I would only buy such a rifle because I liked the rifle, not because of it's cartridge. I own a few 270 Winchesters now and the 260, the CM and the 7-08 all fall short of the 270s Not enough to worry about, but buying a CM as an antelope rifle when I own five 270s doesn't make a good argument.
Buying a rifle because I like it,,,now that's a good argument.
Kragwy said something I really like
Slaves get what they need.
Free men get what they want"
I could not agree more!