Everything I've read suggests that the bluer spectrum of MH is better for vegetative growth and the redder spectrum of HPS is better for flowering. By that I'd say flower with the two HPS.

A lot of this is covered here: http://boards.cannabis.com/indoor-li...uch-light.html
warfrat73 Reviewed by warfrat73 on . what kind of light? I have about five plants that I'm about to start flowering I wanted some info on which lights to use. I have 2 400 watt mh and a 400 hps. I also have a conversion bulb for the mh. Should I use the hps and the conversion bulb with the mh? Or should I use a regular mh bulb and the hps? Rating: 5