You can think of Slick & Slide as an enhanced Detail Spray with the hydrophobic behavior of H2O Guard; however I don't feel it will be as durable as an application of H2O Guard, since I can typically get 2-3 months of protection out of one application of H2O Guard. Slick & Slide is more like a hyper detail spray to add fast and easy shine and slickness to the paint, whereas H2O Guard & Gloss is a water-activate sealant that requires a little more effort to work into the surface. The product line is always growing and evolving, but that doesn't necessarily mean that someone has to use every product - we like to introduce innovative new products to give customers different options when detailing.
For my personal vehicles, H2O Guard & Gloss was my go-to product for many years, but I now find myself using CS3 more often due to its easier application and incredible performance.
As far as where Slick & Slide stacks up in our spray product line, I would say it goes something like this in terms of durability and longevity: