The NEO lineup is sensored - any motor you use with the GTB must be sensored. However, NEO motors do not have thermal sensors on them, so you could overheat and damage your motor if your not careful.
I haven't done extensive head to head comparison between NEO and Velocity. I haven't had any problems with the NEOs with my GTB or LRP Sphere Comp.
My preference is the Velocities. Novak has a new Rotor out (not yet legal), which allows their motors to run cooler. I've used my velocities a lot more (longer run times and more runs). They seem to hold up better. Maybe I had some weak NEOs.