Well, the MDX projectors are a "gem in the rough" so to speak. Do not expect results like this from most halogen projectors.
Most halogen projectors have a smaller bowl, and focus the light more towards the center. a HID projector will usually have a wider beam.
Another problem with the smaller bowl is that it could overheat easier.
Here is my MDX projector next to a H3 projector out of those ebay projector headlights
In addition, some halogen projectors have a weird cutoff. A HID projector is flat with a 'step' in the mdidle. A halogen projector often has more of a slope, which can blind drivers to your right. A halogen beam isnt as intense there, so its ok.
Cutoff comparison:
Plus, as I mentioned before, squirrel finders
But, a good halogen projector can handle HIDs. There isn't a magical aspect that a HID projector has that a halogen doesn't. If you seal up the squirrel finders, give it a good shield, and the bowl doesn't overheat, it works fine.