Torsion bars

Ugh. Yellow, you are close, but you've got to get the "different amount of stored energy" thing out of your head. 72blu is right that both a light and a heavy spring rate have the same amount of stored energy ( the weight of the car) The difference is that the lighter spring rate will assist in weight transfer (or unspring) longer before the unsprung mass (all weight not supported by the springs themselves) works against that weight transfer. So, under the exact same power application, a lighter spring rate and longer suspension travel car will allow better weight transfer before the unsprung mass becomes a factor. You are both making basicly the same argument, but just barely missing the point. The unsprung mass ( wheels, tires, brakes, control arms, etc.) is the only thing that front suspension does ANYTHING for when you launch a car off the line. The lighter rate spring allows all those components to essentially sit on the ground longer while the remainder of the car begins transfering weight