Dave,
Igor always commented on how the failure of many early helicopters was due to the designer seeking the perfection of balanced anti-torque through multiple rotor heads, either co-axial or otherwise. He said, "I believe in one God and one main rotor" only half in gest.
The wasted power hidden in carrying the friction, drag and weight of two transmission load paths, two full sets of rotor controls and/or the propulsive thruster is seldom given, but it is appreciable. The ABC cost 5% of the empty weight for the extra mechanism, and about 5% more drag. kamov has published similar numbers for their co-axials, with drag as probably 10% higher (due to the greater separation of their disks making a higher head mechanism.
In other words, all helos we envision "waste" at least 5% of their power, pick your poison.
I have said before, in the other dozen or so threads you have started on this same subject, that the persuit of symmetry as some mystical goal of perfection is not engineering.