My Understanding is that, with the extra power recoil spring, there is increased inertia when the slide goes forward. The extra power firing pin spring retracts the firing pin a bit faster upon firing (possibly reducing drag marks on primers)and aids in preveventing the firing pin from causing a slam fire if the pistol is dropped on the muzzle. It also gives more resistance to forward movement of the firing pin in order to help overcome the increased inertia of the slide returning to battery under the power of the stiffer recoil spring.