[bri3d]

The size (by cross-section surface area or pretty much any other metric) to thrust ratio is substantially improved, meaning they need a smaller, lighter ball encasing the unit.

I suspect that the thrust-to-weight ratio is also better since they're carrying fewer motors and ESCs around at the expense of some servos and surfaces, which are almost certainly lighter.

Plus the rotors are in a much more advantageous position for containment within a ball.

I'd be interested in evaluating the efficiency of vectoring prop wash using control surfaces versus modulating the speed of fixed-pitch rotors. There's almost certainly something there but I don't know which direction the comparison would go.

Anecdotally it's much easier to get good yaw authority using some type of thrust vectoring (control surfaces, tricopter style tilt-rotor, etc) than using counter-rotation like most quadcopters do as well.

I'd love to build one of these types of machine even sans ball and see how tough the trade-offs vs. a traditional multirotor are in real life; on the surface the design seems superior to me.

[baddox]

Yeah, I realize the advantages of their design, it just doesn't seem worth it with the added complexity and (I would guess) reduced maneuverability. But I guess maneuverability isn't a huge concern, since it's designed to basically bounce around the environment.