It kinda depends on what you want to use it for mostly, that and what you want to spend.
If you want to build one get the FailZero receiver kit and put a top end barrel with a medium twist rate, preferably hammer forged polygonal, and piston kit on it with a match trigger group. That will give the top reliability, accuracy and longevity.
price is what it really comes down to...
Top end: Patriot Ordnance Factory, HK 416, LMT, Noveske, Sabre Defense
Medium: Colt, RRA, Stag, Smith&Wesson
Economy:M&A, Delton, Doublestar, Olympic, DPMS
Any AR can be accurate and reliable with the right parts basically. The thing that matters most for accuracy is the upper receiver and barrel. Easiest thing is to buy a top quality lower and gather uppers as needed