I will use either/or no preference over one or the other.....
Shimano advantage: It can rotate up,down
SRAM cannot do this, this is for noise reduction, however this then means that any slight hit on a SRAM = BOOM, shimano's can take quite a hit an still work.
I personally use Shimano, if I had the money and for some reason my whole drivetrain blew up and EVERYTHING needed replacement I have no idea where Iwould go. I ahve had ride time on X.9, XTR and X.0
XTR is above X.9, and X.0 and XTR are on par, good in some places, bad in others.
One thing Shimano have oging for them, their top line components dont cost anywhere near as much as SRAM's X.0. anything below X.7 is dodgy as all hell and SRAM costs more downunder than shimano