Volocopter has 3 * 6 = 18 rotors in 2 concentric circles, and several different power trains, which run rotors opposite each other. So, up to 4 rotors can fail, and you can still achieve a controlled landing.

If more fails, there's a ballistic rescue chute (which requires a certain altitude).

My gut feeling is that it's better than a piston engine, and comparison to a modern turboprop/turbojet/turbofan remains to be seen. But clearly an electric engine has fewer moving parts.

Edit: Don't know so much about the eHang safety concept, but the whole thing looks dodgy to me, to be frank. The 4 twin rotors don't seem to offer much redundancy, and are conveniently located to chop knee caps... Dunno.

Also, disclaimer: I've invested 1000 EUR into the Volocopter. Thus, I'm clearly biased :-)