4dogs,
I don't think this thread was addressing the natural need for more power (or lower speed) to generate the extra load factor needed in a turn.
You are right, the natural imbalance of the single rotor helo makes the left and right banked turn different. The tail rotor thrust requires a natural right sideslip, and horizontal tail down/upload change the lateral trim significantly. It has been my experience that the left turn needed slightly less bank for a given turn rate, and the right, more bank. Also, the pitch attitude that you trim to is different in each direction, but this varies with the particular helo and its CG, based on how the horizontal tail behaves in the turning flow.
Low speed turns are more affected, since the turn rates are higher, and the radius is smaller, so the turning sideslip is greater.