Hey Ed.
MH, MV and HPS bulbs all require an ignitor and ballast to run. None of which are all that great for UV. MH bulbs will give you more blue spectrum lighting, MV is more yeloow and HPS (High Pressure sodium) is more in the Red Spectrum. There are 4' flourscents that are cheaper then the Reptile version that will work for reps and are used alot in Saltwater aquariums. Don't quote me on this but I believe they are called Aquanetic Bulbs. You can get these at a specialty light bulb supply shop. Just ask for the bulbs used in Saltwater aquariums. They are normally cheaper then the pet world equivalent. MH and HPS are normally used for indoor gardening and MV is what you see in a street lamp. All of them are heavy power consumers normally 150, 400, 600 and 1000 watts and the ballasts in all cases will produce a lot of heat. Only the HPS bulbs can be had in lower wattages, normally labelled as "Security Lights" at places like Rona and Home Depot..and they normally sell for around 90.00 CAD. Best to stay away from the ballast based lights, too expensive for the initial setup and too expensive to run, unless you are planning to do indoor gardening..
Hope this clears things up.
Jim
BTW, controlling the heat (which of course is important for all herps) can not be done with a ballast based light, you can do damage to the ballast itself.