We tested the RaceFace NEXT SL crankset with a single narrow-wide chain ring with a 1x11 system.
This crankset is a work of art. Simple and sleek in design and really lightweight.
The crankset is incredibly lightweight because the crank arms are completely hollow. The crankset a mere 425 grams, which is 137 grams fewer than an XX1 crankset and 156 grams fewer than an XO1 crankset. With that big of a weight save for the price, it's definitely more bang (and less weight) for your buck.
The next best thing about the RaceFace NEXT SL crankset--we forgot it was even there. When we rode with it, it was unobtrusive and unnoticeable...but the bike weighs less. To us, that's a good thing: solid, consistent performance at a reduced weight.
The only downside (other than price) that we can see with this crankset is that you have to remove the drive side crank arm to change the chainring. Not a big deal if you rarely change your front chainring on your 1x11 system, but if you change your gearing often, it could become a pain in the butt. You don't have to remove the crank arms on an XX1 crank to change the chainring, but on the XO1 cranks you do.
I like it!