My short answer is neither: get a 6mm CM for deer hunting. It's a better compliment to your 7 PRC than the 6.5 CM.
If I had a a Delorean and the means to travel back in time, I'd save so much money on centerfire hunting rifles. Instead of the 50 or so I've bought and kept, sold or traded, I'd have just three:
1. .223 Rem
2. 6mm Creedmoor
3. 6.5 PRC
Not knocking the dozens of other useful cartridges, but this battery would cover 100% of the hunting I've done and likely will ever do. Granted, the only "dangerous" animal I've killed was a brown bear with a .338 Win. Mag. While the guide would have flipped out, the reality is the 6.5 PRC and 6mm CM with the right bullet would have done the job just fine.