Slowrotor,
The hovering rotor is more efficient at higher angles of attack. But, as the coefficient of lift increases, so does the coefficient of drag. This implies that, at the initial loss of power, the rotor's inertia will be 'consumed' faster.
You might find the US patent 6,007,298 of interest. It involves using high pitch settings to optimize hover efficiency. It should be noted that the application is for unmanned helicopters.