The leap motion has a limited range, I believe they are currently working on a unit for use with VR HMD as well.
The field of detection on the leap motion is far too low, if you turn your head away from your hands it looses the hand tracking. This would cause issues where when you move your head back there would be a delay to re-detect and then re-position the hands in 3d space. Honestly which ever solution comes to the fore front, it will be the one with the biggest detection sphere and the lowest latency. Competition is good