Nearly a decade ago, Tony Montana and computer mice had one thing in common: they were judged by the quality of their balls. Thicker, heavier balls were better at tracking on your desk, but most people had to use cloth mousepads to get the most grip out of their mice.
Many plastic mousepads have several unfortunate properties: they make your hand sweat like a Brazillian prostitute and they tend to have a sharp edge (amazingly also like many Brazillian prostitutes). Cloth mousepads can be more comfortable because not only do they track well, but they have “more cushion for the pushin’”. Since the pad is just cloth and rubber (I’ve run out of innuendos), there is no sharp edge that can push into your wrist.