After doing tireless research and test drives before finally deciding on my bike build.. I went with a mix or mishmash of SRAM and Shimano..
I got Simano XTR Brake Calipers, Front Derailleur, Crankset and Cassette and I got SRAM XO rear Derailleur (more rugged design) and triggers in carbon fiber.. I also used SAINT brake levers which are basically same as Shimano XT but made of Ti (I believe).
So for me, at least in the realm of the rear derailleur and shifters/trigger the SRAM XO was superior.. but you should prolly test drive a bike or two with different stuff on it and see for your self, and then also read this and
other mtb forums..
I am told the XT and XTR Shimano is all made in Japan, and the SRAM XO is made in Taiwan (not a bad thing), where as a lot of the lower end stuff is made in China or worse..
use the search feature on these forums which is what I did for weeks and read on peoples experiences..
good luck, and share with us what you end up doing.