Pretty much decided on the 6ARC at this point. I will doing my usually shopping around. If I can find a deal on a used Grendel that's significantly better than I can find on the ARC, then I might go that route. But I think the ARC is my choice at this point.
Neither of these will be a bad choice. I have mentioned in the post my favor for the 6 ARC slightly over the 6.5 Grendel, but I voted for the Grendel in the poll. Part of me really likes the 120-130grn bullets of the 6.5mm over the 105-110's of the ARC, part of me really appreciates the extra 200fps.
BUT... when I vote with my wallet, it's the 6mm. I sold my last 6.5 Grendel of my own a few years ago, my son has a 6 ARC, and I have a 6 Grendel (straight neck down, no push back). I've debated heavily, however, getting a 6.5 Grendel barrel and bolt to replace my 6.8 SPC's currently, as I still have 2 of them left, but I just haven't been terribly motivated to do so. The ONLY complaint I really have between them is kind of a toss up of two evils right now - the best powder for the 6 ARC is a relatively terrible powder, and the best powder for the 6.5 Grendel, an amazing powder, is completely unobtanium. Leverevolution promotes great accuracy in the 6 ARC and gives notably higher velocity than other options, but it's dirty burning and incredibly temperature sensitive, which is problematic. Alternatively, 8208 is an absolute dream in the 6.5 Grendel, almost akin to Varget in the 6 Dasher - you'd almost have to try hard to mess it up, BUT, it has been incredibly difficult to procure since pre-covid. Kind of a rock and a hard place to choose between "second best powders" for either of these.
I don't know what the market looks like for used Gen 2 American Ranch rifles, I assume pretty small still, since the model line is only a few months old. But even new, they're not terribly expensive.