Again, a PRC of any caliber is just an improved chamber/bullet design that allows for slightly faster velocities and better ballistics, I'm still not a fan of a 6mm anything in the kind of hunting situations that I'm involved with. If you are a very accurate shooter then I'd say that caliber isn't as much of an issue, you can put the bullet where it needs to go. But in my experience the average hunter isn't that great of a shot, he might think he is but it just ain't so. I consider myself to be a better shot than most shooters and I don't expect to ever have the perfect hunting situation, too many things can go wrong so I err on the side of using more gun than I think I need. A 6.5 CM or PRC is perfectly capable of dropping an elk at any range if you can put the bullet where it needs to go, and those calibers are very accurate (and precise), but in a hunting situation there are just too many uncontrolled factors in play; the animal can move, the wind and temp can vary along the bullet's path, you can flinch because of a cramped muscle, etc. I know that I'm not going to shoot as well in the field as I do from a bench at my local shooting range.
6.5 PRC compared to a 6.5 CM in a competition situation...ehh, I'm not sure you'd see enough difference to justify the cost of building the gun and developing the loads. If you don't have either then sure, buy the PRC, it's a nice cartridge, but if you already own a 6.5 CM, then I doubt if I'd spend the money on a new rifle. I think that the 6.8 or 300 PRC would provide enough change in long range capability that I'd be interested in spending money on them but then that's just my opinion. On the other hand, I would never refuse a free 6.5 PRC if it were offered to me.