What is the difference between sandcarving with aluminum oxide versus silicon carbide?

Though silicon carbide is more expensive than aluminum oxide, it cuts twice as fast, lasts much longer, does not get dull with repeated use (self-sharpens), and does not cause static electricity to build up in the cabinet. A side-benefit of using silicon carbide is that it actually glows when hitting the substrate, which can be used as an indicator of nozzle aim.

-Michael Sullivan, IKONICS Imaging