With XX1 you just get more for your money, which is why it is on both of my bikes:
1) Carbon cranks.
2) Very crisp shifting, XX1 RD moves in a much more optimum path SRAM calls it a "horizontal parallelogram".
3) No need for a chain guide, XX1 locks the chain on the chainring, I have never dropped a chain or experience chain suck.
4) The ability to easily swap the chainring for another size (28T-38T) without the need to remove the cranks. Better suited for racers but a nice feature none the less.
5) I haven't checked the weight, but I would expect the XX1 system to weigh less than a Shimano 1x10 setup.
6) Gripshift or Trigger shift options. I tried the Gripshift initially but decided I liked the XX1 trigger better.
7) 42T rear cog gives great climbing ability.
10T rear cog has ~10% more top end (which is why you need that XX1 hub).
Both offer a clutched, locking RD which is a must have.
BTW, you can't argue that being able to go to "11" is just one better!
Here is a good Youtube video explaining why:
Also, if you have XMIplay build up a set of carbon wheels, they can install the XX1 free hub from the get go so you don't have to purchase it as an extra part, saving $80.
IMO, there is no question that XX1 is the clear choice, however, there are some diehard XT/XTR fans out there.