Colt lower and put together upper for one. My 2nd AR is a gunshow purchased lower and a put together upper.
Both have after market target 2 stage triggers. Both rifles shoot sub one inch groups at 100 yds. and function 100%. The 2nd AR I built up in 223AI (Ackley Improved).
I'll ruffle some feathers here but anyway here goes. Almost all put together rifles will cost a lot less and shot more accurately than almost any factory complete rifle. Just make sure you use top quality parts and match after market triggers. A accurate rifle with a lousy trigger is a inacurrate rifle.
As a friend once said. The lower only serves the purpose of holding the trigger to fire the rifle. And the upper only serves a purpose so the barrel doesn't fall off the lower. It's just that plain and simple.
One must remember that most AR parts, barrel, lowers, uppers are mostly made by a few special manufactures. And just used by other manufactures to build rifles.
My experience of 20 yrs. of shooting AR's for PD shooting out West.