Sole made from crystal salt differes in that it has the essential minerals in it and all of the energy frequencies required for the body to stay healthy.
When you drink the crystal sole you are supplying your body with these minerals and frequencies and the effects last 24 hours so you only need one dose.
I'm not as familiar with the Water Cure but it appears that the reason you use salt is to help you absorb the water better and to also supply some minerals and salt needed by the body. Correct me if I'm wrong though. The crystal sole is meant to correct all imbalances in the body.