Control authority and redundancy* (*yes I will explain this below) are NOT practical advantages this thing has over existing helicopters. The practical advantages this thing has over a helicopter are 1) it's vastly mechanically simpler and 2) very easy to fly (ONLY because it incorporates full authority digital control software, which helicopters can also use--just due to tradition, great expense in certification, and existing high barriers to flying helicopters nobody's gotten around to doing this for a low-cost general aviation helicopter).
Helicopters with semi-rigid or fully articulated rotor systems are capable of really EXTREME control authority provided the craft is engineered to handle the resulting forces. Multi rotors can only dream of doing the kind of maneuvers these helicopters can do. Just look at the RC world.
The multi motor scheme is definitely NOT a survivability advantage and not necessarily a reliability advantage either. Maybe you can have 2 motors fail maximum...at that point, if you have another motor failure and you're more than a certain distance above the ground death is nearly guaranteed! Helicopters can safely descend from most combinations of height and speed under full control with exactly NO engines running. And of course you need to learn the safe height / speed curve for your aircraft, to avoid being in an unrecoverable situation should the engines quit. Now, if the probability of a catastrophic powertrain / control failure (since they're basically one and the same) can be shown to be lower than the probability of an experienced pilot botching his auto after his reliable, certified engine fails...then you have something. I think that may take a while to show, although I don't think there will be a shortage of willing pilots for full digital craft like these.
Efficiency it does not have over helicopters either. The disc loading in a multirotor is rather high compared to a helicopter whose disc terminates at similar dimensions as the multirotor props. And, most human-bearing helicopters run at one speed only, allowing the powertrain to be optimized for that speed. Multirotors, unless they're collective pitch, have no choice but to use drive speed to vary thrust. Then, you have the additional issue that the multirotor props are fixed pitch--they're forced to run at high angle of attack in cruise (or low AoA and very high RPM for low speed flight) whereas the helo disc is big, make a lot of lift, and can cruise at relatively low mean AoA.