If the engine fails in a helicopter, and you have enough altitude, you can autorotate the rotors for a soft landing. It's the helicopter equivalent of gliding i

If the engine fails in a helicopter, and you have enough altitude, you can autorotate the rotors for a soft landing. It's the helicopter equivalent of gliding in a fixed wing aircraft. The danger potential is similar to a fixed wing aircraft - landing and takeoff are the critical stages, but normal flight gives plenty of opportunity for a safe-ish forced landing. A multirotor on the other had doesn't have the ability to glide, like a fixed wing or a helicopter. Any safety will have to be engineered in by making sure that a single rotor failure (or even multiple) can be coped with correctly and reliably.