It is shorter then the XO I can tell you that. It uses a thinner spacer between the BB and the drive side. I think it is about 5mm shorter.
The spacer on the drive side is to lineup the chainline at 49mm. I'm more curious about the NDS. I've seen some BB30 cranks that have a huge spacer between the bearing and the arm interface. I see that XX1 BB30 has the bearing preload. How much slack can that adjust for? Is the axle threaded to use that adjuster?