Every light has a set number of watts that it uses, and a set number of lumens that it emits. Within those lumens, only a certain percentage of them are useful to the plant. Your goal as an indoor grower is to choose lighting that MAXIMIZES how many useable lumens are produced for every watt used. MH is optimal for veg, and HPS is optimal for flower. Flourescents emit the correct TYPE of lumens, but at a higher watt amount per lumen.
Other lights such as incandescents emit a lot of heat along with a bunch of non-useable lumens, and are therefore useless in your grow.