Should I get a PRI Mk12 or high caliber sales mk 12 or a AR 10?

What is the use of said uppers ?

Mostly for fun. And pesky coyotes.

HCS and be done with it. For yotes you don't get any advantage with a .308, much more costly to feed (match grade), and the large frames are harder to shoot. The MK12's are really fun to shoot, and you really can't do better than the HCS offering. That said, I'm biased, but Kevin is a really good guy and I like giving him business when I can. Another option could be to have him build an upper with the same barrel but a muzzle device, handguard, etc. of your choice.

I'm with this guy ^^^.  If you don't have a real need for .308, then definitely stick with the .223 Wylde.  As far as the manufacturers go, I have zero input. I have seen both, but that is it. I know some folks really like their HCS builds.  You probably can't go wrong with either.

For that said purpose, 223 is more than ample.
If you wanna shoot some longer distances just make it an accurate rifle and good quality longer higher bc bullets.
Or ya could always do both