Phosphor electrodes are made with an interior coating of electroluminescent phosphors, which means the glass coating glows when its excited by electricity. This layer of phosphors makes these electrodes glow incredibly bright, up to 5x as bright as regular noble gas electrodes in which the gas is excited and glows.
With the interior coating, phosphor electrodes not only glow brighter, but they make for a stronger spark. Plus they have a great crackling sound. Huge visuals, stronger spark, and a spine-tingling sound.