Haven't heard of mult vapor but
(MH) METAL HALIDE LAMP - A high-intensity-discharge lamp in which the light is produced by arcing electricity through a mixture of metal halides. The light produced by metal halide lamps is in the white-blue spectrum, which encourages vegetative growth and "bushiness" while discouraging upward growth. This is the bulb to use in the first, vegetative phase of plant growth.
(MV) MERCURY VAPOUR LAMPS - The oldest member of the HID family, mercury vapour lamps work by arcing electricity through mercury vapour. While more efficient than incandescent, halogen and fluorescent lamps, mercury vapour lamps are the least effective of the entire HID family. This, combined with an improper colour spectrum for horticultural applications, makes mercury vapour lamps a poor choice for a grow light.