I've made my gradual progression from 6.8 SPC to 6.5 Grendel and finally to 6mm ARC. For general shooting I much prefer the ARC good 6mm target and hunting bullets at useable velocities, at mag length without encroaching into space better used for powder.
Don't know why anyone would bother with 6 SPC wildcats now that the ARC is available, seems like a lot of pain in the ass to get similar speeds with varmint bullets, and not be able to use the heavier bullets at all. More effort and money for less capability, flexibility and industry support.
I don't know anyone who would want to hunt at normal distances with 90 grain bullets out of a 6mm SPC and have a relatively flat trajectory over that distance when they can fantasize about hunting game at 600 yards with a 6 ARC and never have to get away from their computers. And who would be stupid enough to want an extra round in the magazine and have cartridges that feed smoothly? No one, surely.
I've got 10, 15, 20 and 26 round mags from ASC, Duramag and Cprod that have worked fine for me with Grendel and ARC, feed well, I'm not worried about one extra round.
My ARCs have run 85gr, 90gr, 95gr, 100gr, 105gr, 108gr and 112gr bullets just fine, in fact my latest loads have been 90gr TGKs at mag length out of my 18" at a bit over 2,800 fps (best accuracy, but have run up past 2,900 fps). I can run lighter bullets if I want to, it's just not my only option, and I get away from my computer and behind rifles plenty, dick.