i think for the money, you can get something different in a lower, but there is nothing realy wrong with the norc lowers.
ive heard some trigger parts from other brands dont fit right i think it was the pin sizes, but i have friends that bought complete norcs and they all function and shoot perfectly.
if you are building a 10.5 and want a norc, buy a compete 10.5 norc so you dont run into part searching issues, otherwise ide grab a different brand norc lower.
at least, thats what it came down to when i was buying.