When choosing a type of HID (High Intensity Discharge) lighting, it is important to consider the benefits of each.  Metal halide lighting puts off a white type light and is best at providing a daylight type atmosphere.  This type of light is often used in gymnasiums, car dealership parking lots, warehouses, and many other venues.  High Pressure Sodium gives a yellowish type of light.  This type of light is often used in warehouses, parking lots, and for outside security lighting. Most persons prefer metal halide lighting over the high pressure sodium.