Mercury vapor and metal halide bulbs produce heat, bright light, and UVB. They are nice if you want all in one but the downside is that they need to be at a set hight according to UVB output so you may have trouble regulating the heat and need additional heat bulbs. I prefer to maintain heat and UVB separately in my main tank. I do use a good mercury vapor bulb as a portable basking light in the living room though. I'm not as concerned about exact heat gradients there so I just set it 12'' up which is appropriate for the bulb I have and he returns to bask there as needed when he's roaming the house.