Where the later (the Volocopter) is more advanced in its development, I think (they've already had unmanned and manned test flights, and preliminary government approvals), as well as a better concept all in all (what with 18 rotors above the cockpit, rather than on 8 rotors on knee-level).

Full disclosure: I've invested a trifling sum in the Volocopter, so I'm a believer... :-)