There are only three real factors controlling the choice of media: CHow heavy it is, (specific gravity, typically in gcm3) How big it is, (diameter, usually expressed in millimeters or mesh size), What it is made of (strength, wear life, abrasiveness, inertness, cost).Of these, only size and density control its ability to disperse, the other factors being secondary. In other words, for a given size and given density, the material of which the bead is made makes no difference in its ability to disperse.