Hey.... ok there are pros and cons for retrofit AND HID conversion..
1) You have to do 1 more hard stuffs to your car; bake the headlight
2) 100USD more expensive if you are getting the mcculloch HID kit (but it would be cheaper than getting the philips HID kits)
3) You get best output without worrying the cops will catch you or something....
4) You get the blue, purple flicker like BMW/ACURA
5) More works to be done than HID conversion
For HID conversion:
1) You glare the oncoming traffic, but you can always bend the shield(see how-to sticky) to reduce the glare, then again, this will make your lights to shoot more to the ground, and thus you will lose some output
2) 100USD cheaper if you get Mcculloch HID kit
3) Easier to install (take out bumper, headlight, dust cap, drill dust cap, place bulbs, ballast, ignitor, and BAM you got HID), but you have to drill a hole for the wires no matter
if you use a new harness.
4) You dont get those blue/purple flicker
5) Cops will probably catch you if he is having a bad day (like have a fight with his wife/gf
6) It's easy to convert back to stock if you want to sell your car
7) Unreliable warranty. (as it will get broken easily if you are not using some ballast/ignitor from those high-end car such as BMW/ACURA/AUDI) Philips is reliable, but they denied of having aftermarket HID kit.
But then again, these comments are basically depends on you, as i did retrofit opposed to HID conversion. So probably it's kind of bias
. My advice is that, if you dont have that much time/nice warm garage, then probably HId conversion is the best for you. But as i said, for a measly 100USD, you'll get to know your car + you get a real Xenon without worrying getting pulled over by cops + you wont get anything good for your 6 for that kind of money (cp-e? magnaflow? not even AEM
). Just my $0.02.