Buy a good digital like lumatek, or the equivalent. Texas Hydro has been blowing some out lately. Use a good bulb like Digilux or something that's made for digital ballasts. Search hard... I found my Digilux 1000Wer's for $76.00 each! If you have the cash do it right. You'll save in the long run!
HPS lights do vary slightly in measured spectrum/color output, but you should use MH for veg and HPS for flowering. IMHO!