I found this in a new article on Hybridcars.com about using capacitors and batteries in the hybrid system. It appears to support the idea that we should be braking slowly rather than hard to stop quick.

If you push a battery too far, it can overheat. Therefore, there are limits to how much power a battery can handle when charging. Think of a battery as a huge tank with a thin hose connected to it. The tank can hold a lot of water, but filling and draining it takes a long time compared to that small air balloon, which can fill and drain quickly.

Prius 06 Black Pack#2