Don't have either at this point, but the 6.5 Grendel eats the 6.8's lunch pretty much across the board for varmints, medium game, and especially as a long-range cartridge. It fits the same platforms as well. A fast-twist .223 also surpasses the 6.8 for a lot of purposes, I think, and has mountains of available rifles and cheap ammo and components.
All that doesn't mean the 6.8 isn't worth owning and using, just that there's better stuff out there. It probably doesn't help that the 6.8 is a stubby little number that looks kind of dumpy compared to the sexy Grendel.
Another issue for me is that 6.8 brass is an odd duck, and given what we've been through the last few years, feeding one could become problematic in a pinch.
