Projectors will make the enjoyable of HID lightning work at its maximum potential. Projectors control the ammount of light on the road but you may be asking HID bulbs shift light everywhere? how could a projector enhance the performance of my HID bulbs? Well, there's this thing built inside the projector called "shield". A shield will control the shifting of light thus producing a beam with the maximum light possible to the road. The projector itself can be adjusted and you have the maximum light output at its maximum potential.
1) HID: High intensity Discharge lightning that produces an arc shifting light everywhere. In other words, this means that light from HID is basically uncontrollable. It shifts up, down, left, right. But what are the advantages and consecuences of having HIDs in your car?
A) OEM Projectors with HID's. These come in luxury cars. Great output, and road visibility is superb for those with poor visibility or weak eyes. If you love the look of it, then this is a must for it not only enhance visibility but the colorful cut-off makes you scream how could that be possible? The trick is in the lenses itself but I'm not gonna get into that here.
HID kits on ebay and elsewhere which claim to "enhance your light output on the road like true HID with projectors from luxury cars".
Reason why I hate pnp kits is that they lie their butts off to sell such hazard products which put in danger innocent lives while they make a profit out of it. Products which are sold for 100, 150 and/or 200 are just garbage. If you want a true pnp hid kit which will not have as much glare as others will be a good 400+ kit. Remember, you get what you paid for.
As I said before, HID bulbs produce an arc of light which shifts in every single direction: up, down, left, right. However, if you put a pnp kit in a halogen housing(reflector), you will have the effect of an HID without projectors, thus making that high intensity discharge lightning work to its minimum. Why? Reason why HID bulbs do its job shifting in the +/-x, and +/-y. You cannot control the shifting with a reflector. It has NO shields. This will case in glare coming from every single spot of the headlight. In other words, scattered light will be coming out of the headlight. This is the main complaint about pnp HID kits.
Pros of having a pnp kit: It will light up the road twice as a normal halogen will. You will be ab le to see road signs clearly.
Cons of having a pnp kit: widthness of light output isn't great. True cause of using an HID will be misinterpretated. Glare to oncoming traffic will be alot causing yourself to be a road hazard on wheels. Reducing the glare will in fact make your headlights aim down the ground more than they should which will backfire you. This backfire will be the loss of light output further down the road. IT IS ILLEGAL IN ALL STATES.
Now, draw your own conclusions and if you want a get a pnp kit because you want to improve your night-time driving and don't want to spend lots of money on retrofitting, then by all means go ahead but before you decide to get one, do your research and do it right. Get one that has a known brand name and is also known for reducing glare. If you decide to save money and greatly improve your night-time driving, then a retrofit with oem projectors is your best bet.
There are many great retrofitters in this website.