Is it better for a suspension to have soft coil springs or stiff springs? The purpose of a suspension is to keep your tires on the ground. A softer suspension will offer more mechanical grip as it will do a better job of keeping the tires on the ground vs a stiff suspension when it comes to depressions, bumps, and surface irregularities in the road. But then why do race cars have such stiff suspensions? This video explains the design philosophy behind race car suspensions.
Related Links (And Hat Tip!)
Race Car Design by Derek Seward - http://www.amazon.com/Race-Car-Design-Derek-Seward/dp/1137030143