There are many many different AR's in the Market. IMHO Colt is great, but yes pricey. Daniels Defense, DDM4 great yes very pricey. Wilson Combat and Bear semi customs are amazing and farther out of sight, even more pricey. I always favored my Bushmaster and RRA LAR-15. The RRA has that sweet two stage trigger and is built like a battle rifle, it will shoot lights out at 100 yards. Stag & S&W are good mid range and can also get pricey.
It depends what YOU like. By the way Colt just came out with a new LE6940P Piston Driven Powerhouse built to be the next generation M4. This incorporates Colts new Articulating Link Piston (ALP) operating system. Without getting complicated it deflects thermal gases, and ease of cleaning.
A really cool, if you have the bucks is the Colt LE6920MP, It comes with about $220 worth of Magpul accessories, everything you THINK you ever wanted, for about $1228.00
Remember you can trick out your AR15 with everything under the sun. I am still partial to the RRA LAR-15, and Bushmasters, and they cost less. Just MHO..
Regards PAH04