metal halide and HPS are both types of HID, MH bieng better for growing, HPS bieng better for flowering.

either can be used throughout the grow, but each is lacking in certain colours, which is why if you have the money, you can get both for better results.

if your only going to get one light, i would recomend an "enhanced" HPS light, which is "tuned" somhow to give extra blue light which regular HPS lacks, im using one and so far ive got nothing but praise for it.....it looks a bit closer to natural light than a regular hps, but still has a bit of a yellow glow to it
babystarbud Reviewed by babystarbud on . HOW MANY PEOPLE USE CFL AND HOW MANY HPS OR BOTH? WHICH ONE IS THE ONE TO USE WHEN VEGGING WHICH ONE WHEN FLOWERING ANY HELP APPRICIATED. Rating: 5