Hmm yes I knew this... actually, I think SE or mogul based bulbs are filled with an inert low expansion gas. I was just curious if one was different than the other, like if the light spread is different or what?
Upon further investigation, I think that a DE bulb (thanks asmodeus you got me thinking
) is actually the same as a SE bulb but without the glass envelope. So really, 2 bulbs made by the same manufacturer and with the same elements but one being SE and the other DE
should put off the same quality of light.
HQI refers to how the bulb itself is built (Hydrargyrum Quartz Iodide). There are also HMI (Hydrargyrum Medium-arc Iodide) and other types of HID lighting systems, but they share the ballast and arc-tube design.