Re: bushmaster or cmmg which one??????????
Over at ar15.com the consensus is that DPMS makes CMMG's guns.
My brother owns a Bushmaster M4 and it has been an excellent firearm. No failures thus far- but only 600 rounds through it at this point. It seems to shoot fairly well for what it is, 1.5" 5-shot groups with Federal ammo.
Personally I'd go with whatever one you can find in stock.