Back to the OP, original question, 25.06, or 6.5 creedmoor.
I will start by saying, that a well loaded 25.06, will flat kill a deer, at distance, as well as some overbored,magnums, and the deer dont care. I personally, have killed a PLENTY, of deer with it, and have tracked none. Thanks to Barnes. So, enough on that subject.
As to the other option, 6.5 creed, all else being equal, meaning standard twist rates, and bullet weights, there is a point that the creedmoor will over power the 06, down range, due to 6.5 being able to stabilize a heavier bullet, due to the 1-8 twist, whereas, the standard twist for the 06 is 1-10 which makes it top out at about 120 grains.
Which also brings about a interesting scenario, if you shoot 120 grain bullets out of each, the exit velocity is about the same, but the the six five , having the higher bc, will have less drop.
So, my take was to keep it more apples/apples. And the six five, is in a short action, with tons of awesome ammo, IF, you don't reload.
I love an 06, it is truly Badass, but , I feel the 6.5 overshadows it slightly, more so, its a short action to boot.
JMHO,