Metal Halide vs. High Pressure Sodium
It’s relatively impossible to compare metal halide and high pressure sodium lights to decide which one is better. Both of them are equally effective because your marijuana plants will need them for different stages of plant growth. Make sure that you know which type of light is needed for which stages and why it is better for that stage.
This light emits a lot from the blue area of the light spectrum and is preferred for the vegetate state of growth. The light that you get from metal halide lamps can be comparable to cool white fluorescent lights which are used in various school, stores, offices, and other places with many people around.
High Pressure Sodium
This light emits a lot from the red area of the light spectrum and is preferred for the flowering state of growth. The light that you get from high pressure sodium lamps can be comparable to warm incandescent lights which are used in certain homes and street lamps. A lot of home lights that are comparable to this light may have a tone of dark orange or red though.
Due to the facts that are provided you can conclude that you will need both lights. You want to mimic what the sun does so you will want to use the metal halide during the early days of your marijuana plants growing and you will switch to high pressure sodium once the marijuana plants are almost fully grown.