Stag and Spike's both have a good reputation. Spike's takes it a few steps further compared to some of the other AR manufacture's. This chart gives you idea of who puts more detail in their rifles. Spike's isn't listed in the charts but they do put alot of detail in their rifles. Personally I think Spike's or maybe a stock M&P15 would be my choice. Not to say that the rest are not good.
http://www.google.com/search?q=ar-15...ed=0CEUQsAQ4Cg