Does putting the Prius shift in the B position recuperate more energy to the batteries than use of the brake to retard the car when going down a steep hill?

AnswerNo, it does not.

Regenerative braking occurs when pressing on the brake pedal gently, up until the hybrid battery is fully charged. Once the battery is full (all bars full up green), the Prius computer switches to using mechanical braking only. On very long down hills, this can cause the mechanical brakes to overheat and lose effectiveness.

The B position makes the hybrid system use engine compression to slow the car, which saves the brakes, just like on a regular car with an automatic transmission.

Only use the B position when the battery charge indicator is full up green. Using it during normal driving simply adds wear-and-tear to the engine and reduces gas mileage.

AnswerThe B position serves just like lower gears in a normal car, and it's really only there to slow the car when you will be descending a long enough hill that you would have to constantly apply the brakes. It doesn't recharge the batteries in the car any better than the normal brakes do, it's just there in the case of situations like long, mountain roads and the such to keep the car from gaining too much speed and keep you from using the brakes too much.