6.5 PRC give you some room to make a mistake on a wind call or distance and gives you more energy to cover a little extra yardage. I use the 6.5 SAUM and its a great round, the PRC is just the commercial version of that. You can get 156gr bullets moving < 3000 fps and they are like a freight train on WT deer. 6.5 PRC also lets you move up to bigger game if you decide to, but either cartridge should be fine for your purposes.
Where I grew up in PA, we had 1000 yd shooting ranges and 1000 yd shooting leagues. I know guys that hunt elk and deer at long ranges and sometimes over 1000 yds but they have very specific equipment to do that, shoot year round and hunt in groups off tables with heavy rifles, rests and wind flags. They also are shooting at bedded or standing deer, with snow on the ground. Not my style of preferred hunting. I have a rifle set up for those ranges but I seldom use it.
I normally limit myself to 400 yds in the field and I've passed on more shots at that range then I've taken but to each their own. I prefer larger calibers but if was buying a 6.5 it would probably be a Creedmoor.
I suggest getting on Facebook and finding a good blood dog in your area with either. 6.5’s aren’t made for thick southern woods. I agree with the fella that posted above, I’ve yet to get a blood trail from 7 different bullets in the Creedmoor on kills from 50 to 760 yards.
140gr Hornady Black used in a bind because I was moving and my reloading supplies were in storage.
6.5CM
10 yard shot, ran 50 and piled up. Insane blood trail. Picture is of the exit wound, probably golf ball sized.
I laugh when y’all get on here and say XY caliber is inadequate for deer hunting, poor blood trail.... I’ve tracked heart shot deer with a .308 that never bled. I’ve watched deer DRT with .223’s more times than I can count.
Quit blaming the caliber and look at the SHOOTER.
OP I’d go CM just for ammo availability. Either cartridge is more than capable for Southern deer that can be 100 up to maybe 200# live weight.