Well in my experience mercury vapor bulbs that are sold in the pet industry don’t really give off the kind of basking temps you need for dragons. They are mostly flood bulbs and they are sold in 100 watt or 150 watt. If you go to a lighting store you can get spot mercury vapor bulbs but the wattage is way to high. Mercury vapor bulbs are really intended to provide UV.
Halogen bulbs really do work great. They are brighter and last longer than incandescent bulbs but they are a hotter running bulb. If you have a “reptile room” with a lot of lighting, halogen bulbs can really increase the over all room temp. I really do like halogen bulbs but keep in mind that they give off no UVB.
I would really recommend using a florescent tube for your UV and either an incandescent or halogen bulb for the basking spot. Pet stores sell great UV florescent tubes that are proven to work like Exo-Terra or Zoo Med and they can be used with timers unlike mercury vapor bulbs. But don’t forget the calcium with D-3…