The water or solvent is the “carrier” used to dissolve or transport the different sealer resins. Hence it is possible for an acrylic sealer or silicone repellent to be both either solvent or water based. As a general rule solvent based systems tend to penetrate better than water based systems but will generally darken the tile surface. The exception is repellents where there is no real difference. Quality is determined by the type of polymer or resin, not by the carrier.