Electroplated disks have diamonds that are locked into place with a layer of nickel that is grown up around the diamond in a chemical bath. The diamonds are rigid and will give a very aggressive grind on your glass. These are generally used for rough grinding to a finer grind, but will not give a pre-polished surface and generally cannot be polished out.
The Electrostatic diamond material from 3M is an adhesive bonded diamond material.
The backing material has a high grade adhesive applied and then the diamonds on the surface are electrostatic-ally charged. This makes the diamonds "stand up" on the surface of the material as the adhesive cures. There isn't any nickel holding the diamonds in place, instead they are held on the surface with the adhesive.
When the glass passes over the diamonds, they will bend slightly in the adhesive to give a smoother grind than the typical electroplated diamond would. Since they are all standing straight up, the grind is fairly aggressive, but ends up giving a surface that is quite clean and smooth and can be easily polished from in the finer grits.
Because of the nature of the material, electrostatic diamond material will last far less time than the typical electroplated diamond, but they will give you much more control over the surface grinding and a much better surface when you're done grinding. They are excellent for working smaller surface areas where control and surface preparation is more critical.