P7 just refers to the LED emitter (sort of the equivalent of the light bulb). You can put it in many different kinds of lights- DX alone has at least 4 or 5 and probably a lot more. The quality and utility of the light will vary a lot with the reflector, lens, etc. There are lots of threads comparing the lights on here. FWIW, the DX 5 mode is supposed to be better than the DX 8 mode. Another kind of LED is called the Cree. Some think it's better than the P7, but hey are pretty close.