Your original equipment headlights are good for a lot of conditions, master of none.
Bulbs/Wattage: Measured in watts; higher wattage means brighter
light. (except for HID metal-halide systems which project the brightest
beam available at relatively low wattage.)
SEALED BEAM (Incandescent)
The vacuum sealed beam was the traditional automotive light source for many years.
For many applications such as marine, it remains popular due
in part to its complete atmospheric sealing which keeps water and
condensation away from the interior of the light. Bulb life is typically less than a Halogen or HID light source and the Color temperature
is approximately 2700° K.
QUARTZ HALOGEN
A very widely used light source due to its relatively low bulb cost, good bulb life
and whiter light temperature of approximately 3000° K.
HID - HIGH INTENSITY DISCHARGE
This exciting automotive technology uses mercury and xenon gases
to create and maintain a light source. These two gasses are ignited
by applying 30,000 volts of current (provided by a Ballast) to two electrodes within a glass
tube about the size of a green pea. HID lighting is extremely durable and draws much less power than traditional sources. KC HID's produce a whiter light source that is more than three times more powerful than a halogen source and attain a color temperature of 4200° K (actual daylight is around 5500° K).
Lens: Most critical in determining
clarity, focus, and beam pattern of any light. Plastic lens are common
in low power lights; glass lens are required for high-power lights.
Amber or Clear? Clear lens pass more light to let you see better.
Amber lens provide more contrast and let the other drivers see you
sooner. Amber is more easily seen in fog or snow.

Housing: Casing which contains the bulb and lens. Can be made
of ABS plastic, aluminum, chromed steel or stainless steel. Some housings
have "shock mounting" for severe conditions.