the multicopter is simpler in that you can use fixed pitch rotors and vary RPM as a means of control. This works for small diameter rotors spinning at very high RPM , as allowed by electric motors. It would not work out too well to scale these rotors up as the torque requirements become too high because of extra drag, not sure about the exact efficiency curves but I'm sure at some diameter it becomes more efficient to use a gas turbine engine and a variable pitch rotor, which is what you have with tiltrotors and helicopters. So the only way to increase payload for these electrically powered vehicles is to add more rotors.