HI AOD
This can be complicated, mostly because the companies manufacturing the lights make it that way. When Zoo Med (ReptiSun) and Exo Terra (Used to be ReptiGlo, but they now make the same lights in new packaging since they have been found by most people to be inferior to the ReptiSuns), first came out with these lines they labeled them 10.0, 5.0, & 2.0, corresponding to 10%, 5%, & 2% UVB output, respectively.
Th Zilla line I have never figured out, and have heard generally bad things about, either in life of UVB output, flashes (brief overexposure of UVB), etc.
There are three basic types of Bulbs, fluorescent tubes, compact fluorescents, and mercury vapor bulbs.
Fluorescent tubes are just like they sound. They are usually placed the length of the enclosure, in a method some people have called "shading", meaning the entire enclosure gets mild UVB enclosure, as compared to one area getting concentrated exposure only. This is the method I prefer, and have seen the best results overall with.
Compact fluorescents, coiled fluorescents, etc, Are actually the same basic type of light, (fluorescent) but coiled and attached to a disposable ballast that can screw into an ordinary incandescent socket. These are problematic. First, the light is generally more intense, as there are 3 or 4 strips of fluorescent light in a row facing the same direction, and if you put it in a reflective dome, the results can be even worse. They can work, but you need to very careful with placement and distance. If there is too much UVB, the animal may avoid the area, or sit there and have other problems (i.e. blindness). And if they Have a flash of extra UVB...
The Mercury vapor bulbs are an incandescent spotlight/floodlight that also produces UVB. And they do seem to work in a more natural way. The real problems here are cost (the good ones are expensive) and fragility, they burn out easily. Any drip of moisture, sometimes even oils from your fingers,and they can go out... If you want one of these the Flukers Sun Spot and the Zoo Med Power Suns have had the best results, with the longest life.
Personally, I like the fluorescent tubes, the entire length of the cage. I use either ReptiSuns or the Arcadias. You want a high output, a reptisun 10.0 or the 12% Arcadias. Then I use a separate incandescent floodlight for heat. Here are a few links with info, as well as a good place to look for them.
http://www.uvguide.co.uk/
http://www.beardeddragon.org/articles/uvintro/
http://www.beautifuldragons.com/Researchmain.html
http://lightyourreptiles.com/
