I think 6.8spc is a cool caliber, but realistically it's been swallowed up a bit by 300blk. I know a lot of AR nuts who will tell you plain and simple, that 6.8 is a "dead" caliber because of this. I'm not going to tell you this is right or wrong. But there's enough of people who feel that way to impact the supply and thus the price and future ammunition options for this caliber. Just something to consider.
For my own needs and practicalities: 223/556 > 308 > 300blk > 6.8spc
Just preference. Again, I like the caliber. It just might be a spendy and limited endeavor going forward. From what I've seen I'm also not a big fan of Ruger's offerings in this department. Piston = heavy, with limited compatability IMO. There are some great piston ARs out there, but most of them will set you back as much as a decent used car.