China manufacturer of magnetic ballasts for metal halide flood lights & hps flood lights

High-pressure sodium (HPS) to metal halide (MH) street lamp installations based on their perceived brightness, safety, support of social interaction, and ability to support facial recognition and eyewitness identification.

HPS lamps are the most commonly used lamps for outdoor applications due to their low initial and operating costs; more recently, however, MH lamps are also being used because they are comparable in cost to HPS lamps and are perceived as more inviting. However, some aspects of lighting “quality” cannot be objectively measured.
A primary objective of outdoor street lighting is to improve security by supporting visibility of facial features. This underscores the importance of light level and light source color rendering in creating a sense of safety in outdoor environments. However, research has not considered these factors.

High pressure sodium lighting may be more efficient and needs to be replaced less often.  People who are concerned about the environment may choose either type of lighting. However, HPS ballasts tend to last longer. This means more convenience for you because of less frequent replacement. It also means better news for the earth since it takes longer for these lamps to end up in landfills.

HPS lamps are available in color-corrected versions that shorten their life and only slightly improve color temperature. Even with greatly improved CRIs, the color temperature still delivers yellow light. This color limitation is present because the HPS lamp generates light through the excitation of sodium. Metal halide lamps, on the other hand, generate light through the excitation of 2 to 5 different chemicals in the arc tube. In addition, the exclusive Uni-Form formed body arc tube is a newly-designed, compact light source sculpted to follow the physical shape of the arc itself. The precise geometry of this unique arc tube, accurately reproducible from lamp to lamp, produces a metal halide lamp of greater efficiency, improved color uniformity, and longer life.

HPS is sometimes preferred for outdoor lighting.  The reason for this is that night vision tends to be affected more by the metal halide lighting than by the HPS lighting.  If you have a group of people outside under lighting who also need to see things that are going on outside of the lit area then you might want HPS lighting.