jrj,
What a meant was I would concerned about barrel specs, forend style, sights or lack of, trigger (cmmg has a match trigger now), BCG (style, coating, chrome?).
I would compare those type of things. I have had both manufactures and CMMG treated me well. I actually used their warranty on a piston set-up I messed up. But, I would compare components first.
I hope this helps.
Blessings,
BC