I get dizzy about half an hour into using the HoloLens. I am not sure why, I think it may be because the tracking/rendering doesn't quite keep up with fast head motions making the holograms "inconsistent" with the real world. It might also be that it's because of the accomodation/convergence mismatch ...
Not to mention that Magic Leap's multiple depth-of-field display will likely simulate normal vision much better than current-generation VR displays, and that there's no artificial locomotion in AR.