I use the Xenon, bulbs. It is a nice cheap upgrade. I like the brighter white light. The hot spot is smaller and much tighter. The spill is not as nice. And for some reason when you move the light to fast it gives the appearance on the wall of flickering. It is NOT actually flickering as I have tested it time and time again. Bit on certain color wall running over like ledges or the outside of frames you notice it. Run time appears longer as well, not like an LED upgrade. But for three dollars, I think it is a nice choice. I really think these bulbs should be stock and not an upgrade.
I have a 3 D that is running this bulb. I am going to switch out the lens and that will be all for this light. I am going to do the Terrlux upgrade with lens and reflector and possibly batteries to my one of my other 3D mags. The other D celss I am not sure what I am going to do with them. I am more into the smaller lights.
I hope this help. If you want a cheap, easy, noticeable upgrade for less then 5 bucks, I would say that the Xenon is the way to go.