..........the HPS that is good for growing is called GROLUX.....GOOD entry level is 250 watts.......with GROLUX you grow BOTH cycles (VEGETATION and FLOWERING).....they are made so as to start and finish a grow with good results (they have RED BLUE & ORANGE spectrum) .....
MH bulbs are the BEST for vegetation because they contain mainly (if not only) the BLUE spectrum of light (plants use that in order to grow tall and large)
......now.....there are other HPS lights as was mentined above and not all of them are for grow......another good type of HPS is the SHP-TS which is better to be used for FLOWERING.....it is furthermore enhanced in ORANGE&RED spectrum of light (plants need that in order to produce large and thick flowers that we stonners refer to as BUDS full of trichomes)......so....now search for GROLUX, SHP-TS and MH bulbs.....