alright i get asked this all the time, so i figured id make a post to try and show the differences. My camera sucks and so do my photog skills. i will try and show the difference between stock halogen, ebay hid and good quality hid kits.
these are all taken same car, same place in the driveway. first is stock halogen. second pic is ebay hid, last is a good hid kit.

Stock Halogens

Ebay HID's

Good HID's
As you can see both sets of hids are equally as bright, much brighter than the halogen. the ebay ones are a big ball of unfocused light. this blinds other drivers, and really pisses off cops. the light is diffused, and does not go very far at all. the good hids have a nice tight beam, the cut off is exactly the same as stock, focal point same as stock ad they penetrate much deeper into the darkness without blinding on coming traffic.
The couple of bucks you will save on ebay you will end up spending on tickets, or having to remove them because you constantly get messed with by the cops or are tired of people flashing you.
PM me if you want to get your hands on GOOD HID'S