HIDs Explained.
HID vs Stock
Here are just a few examples of the contrasting colors the stock (Halogen) bulbs put off, compared to the HIDs(
There are various colors from 3200k raning all the way up to 10000k (Kelvin = color measurement of light)
The color chart may be somewhat relevant to you, here is an example:
As you can see, the color tone is measured in kelvin (xxxxK).
In a normal headlamp, there is a small bulb roughly the size and shape of a pen lid. It is in essence a very bright version of the glow-lamp you would use in your house, not all that different different from the lightbulb invented in 1880s: A filament gets heated by electricity passing through, and the heat causes light emission. Modern headlamps are normally Halogen lamps - the inside of the bulb is filled with Halogen gas, which allows the bulb to burn at a higher temperature, and therefore brighter.
Xenon headlamps are technically known as Xenon HID light. HID stands for High Intensity Discharge, and refers to the technology involved. Instead of a glowing filament, the light is generated by a spark which jumps across a gap constantly - just like a constant arc of mini-lightning.
More, but not better light
The light output from a Xenon headlamp can be roughly four times more than for a standard Halogen lamp, and the colour of the Xenon lights are a lot closer to that of daylight. Industry experts disagree if this is necessarily a good thing: At night, your eyes adapt to the warmer tones of the motorway lighting and other drivers, and the daylight-colour of Xenon lights might be problematic, as the eyes may not be able to register colour information correctly. In addition, light from Xenon lights is of very specific colours, rather than a continuous string of all colours of the rainbow.
In addition, the optical physics behind creating an Xenon headlamp are very different from "normal" lights, which means that replacing the unit could be very expensive indeed.
On the other hand, because the Xenon lights give a higher light output than their halogen equivalents, it allows car designers more freedom in designing unique-looking cars which still fulfill the needs for strong light.
So, should you choose Xenon headlamps?
In theory, Xenon is a good idea. In practice, more light doesn't necessarily mean that the quality of your night-vision is any better. In fact, it may be worse: The fact that the light is so bright could make your eyes adjust to the brightness. This means that you can see perfectly right in front of your car, but especially on wet roads, the glare may be tiring and problematic. In practice, despite the light being brighter, you may not be able to see further in front of you at night.
On the other hand, the Xenon headlamps do look the part, and cars designed especially for these HID lights can look better than their Halogen counterpart. New technology is on the way, however, and it won't be long until we will see high-intensity LED headlamps, which might solve many of the problems the Xenon lights are currently experiencing.
If you have the choice, and you value safety over looks, you may as well stick to the Halogen lamps for now.
HID kits are readily available throughout many many stores as well as ebay and craigslist. The *real* kits range anywhere from 150-500+. If you are going to get HIDs be warned, they ARE ILLEGAL unless you have a dealership/automotive store install them and mount them, though it is simple enough for you to do it yourself, you just splice two wires off of your stock harness after mounting the box and mount the ballast, and away you go!