Efficient. They put out more light, with less energy usage, than any other type of illumination available to indoor growers.
Bright. HID's produce more light than other types of indoor horticultural lighting.
Expensive. HID's cost more than flourescents. They range in price from $50-$600 dollars.
Hot. HID's produce considerably more heat than standard fluorescents.
Fluorescent lamps are:
Inexpensive. Shoplight fixtures can be purchased for as little as $7. Compact fluorescent bulbs only cost a couple of dollars a piece.
Locally Available. Most discount stores and home improvement stores carry inexpensive, fluorescent fixtures and bulbs.
Fine for vegetative growth. Fluorescent bulbs put out plenty of light for plants growing vegetatively, including mothers, seedlings and clones. Some growers prefer fluorescents for vegetative growth because of the slower pace of growth and better root development.
Fluorescents need to be in close proximity to achieve their rated output, which means their canopy penetration is more limited than HID's.
Comparatively inefficient. 10 forty watt fluorescent bulbs use the same amount of energy as a 400 watt HID, but produce far less light. Since they use the same amount of energy but produce less light, the remaining must be given off as heat. Contrary to how it may first appear, fluoros actually run hotter than the equivalent wattage of HID-- they just disperse the heat over a wider area.