How about $500? lol
Is there a significant difference? Yes. Price wise, you're buying OEM stuff so there is more reliability than if you get aftermarket stuff and you won't have to worry about constantly replacing bulbs because it blows up. If you do find the need to purchase new bulbs, they are $75 shipped for a pair (
http://www.hidplanet.com), whereas with aftermarket kits you have to buy kit specific bulbs that can cost more than $200 for JUST the bulbs!
Light output? Of course projectors will give you more light output! It will also be more even and have a nice cutoff so that you're not blinding other people. Halogen reflector and projector headlights have to narrowly focus the beam so that any and all available light can be put up front. With HID there is an excess of light coming from the bulb, so it can be spread wider and further down the road.
Now send me my points, damnit!
