Torque Boxes vs. Frame Connectors

On another thread someone suggested I consider adding torque boxes or subframe connectors to my car. It made me start to think about whether or not a person needed both or if the subframe connectors would negate the need for the torque boxes. Is one superior to the other. I assume that Chrysler did not tie the frame rails together because of the unibody mind set. - It would have probably sent the message to people that the unibody was weaker than a full frame.

Do the torque boxes actually reduce the amount of twist to the body or do they just strengthen the areas where the leaf springs attach?