Dunno... Shimanos tend to have more flex and therefore have more ability to bend before snapping. Thats why you see a lot of snapped Srams compared to Shimanos. That said, i' been running my Sram XO setup for a while now and have yet to encounter any problems. Plus, the SRAM triggers just feel very natural with the thumb shifting and the shifting is clean and crisp... Love it...
I've use both Sram and Shimano driveline components and Shimano has the edge right now.
Shimano's chains and cassettes have been better than Sram's for at least a couple of years now.
Shimano's Shadow XT derailleurs are great in technical terrain. Shimano has taken the Shadow derailleurs and designed them so they don't slap the chain stays anymore and the return springs are tighter, so you get more positive shifting with full length housing.
The spring that tensions the cage is also firmer on the new Shadow groups. This helps with chain slap.
Right now, I honestly think, the XT Shadow group, has the edge on Sram's X.0 group.
I know the original question was XTR vs X.0, but the new XT stuff is so much lighter than it was.
Also; XT is Shimano's strongest group, except for Saint or the XTR cranks.
"I thought of that while riding my bike." Albert Einstein, on the theory of relativity.