Silly question: could it have anything to do with the "lenses"?
Sorry, I just couldn't resist. I don't have any specs on the two units but if the one has a "High Discharge" bulb and the other is just a regular halogen then yes there is a diference in the two. High Discharge is 1.5 times brighter in lumens than the regular halogen (I think it's 1.5) anyways, look at driving lights you have three categories sealed beam (kinda like a par bulb) halogen (kinda like the in most light fixtures) and High Discharge Intensity (low wattage extreme output)In a moving head you would most likely find a halogen bulb. In a projector (newer ones) you will find a HDI bulb. The reason for the HDI is so it can project at the same intensity (lumens) that a higher wattage halogen can without the same heat and power consumption. If I am wrong please correct me it has been a while since I had to play with HDI...
Rage