A good friend of mine has been using 6ARC lately on ground hogs and coyotes and loves it, he has been hand loading the 90 gr Sierra Game Changers. I have used it a couple of times and have been impressed with it, but for the distances that we typically hunt (300 and in) I stick to my 223.
I have never shopped for factory ammo on 6ARC or 6.5 Grendel, but if you are not planning on reloading for it, I would shop around and see which has better availability and go with that.