Vegetative Grow Lights
There are many different types of grow lights from propagation grow lights which would be cfls, T5 propagation lights and metal halides. Metal Halide bulbs come in a few different sizes. Popular sizes are 400w, 600w and 1000w. You also have your flowering grow lights like Digital Dim-able 600w High Pressure Sodium Lights. In your early stages of propagation or vegetative stages it would be better to use a cfl or T5 light. These lights are better for early veg stages as they do not produce a lot of heat and the levels of light are not to intense for the plant. They produce a good spectrum of clean light almost mimicking the suns daylight, perfect for small plants and cuttings. Metal Halide bulbs can be put into your 600w dim-able ballasts but would be better used for a mother plant or later stages of vegging.
Flowering Grow Lights
Same again as the vegetative lights there are also many different flowering grow lights from your latest LED grow lights that have hit the market to your standard HPS 600w grow light. You can literally get all different powers ranging from 150w all the way up to 1000w. The power you use usually depends on the size of your grow room. Small rooms we would recommend lower power lights. Big spacey rooms can handle higher power grow lights like the 600w HPS and 1000w HPS. If heat is a real issue use LEDs or put higher power fans to help with heat issues. Another method is to combine different power grow lights together in the room mixing HPS with LEDs or High pressure sodium's with the Philips Daylight range which are half the power but kick out some good lumens. Grow It Yourself Hydroponics Growing tip Remember to change your bulbs after 9 months of use with HPS as they will begin to decrease in performance.