I don't grow hydro, so just on the light question:

Generally (using standard bulbs), MH is better for vegitation and HPS better for flowering.

I've grown using a 250 watt MH and then I switched to a 400 watt HPS and a 1000 watt HPS. I would recommend an HPS if you had to choose one for the whole grow.

Best of both worlds would be both or an expanded spectrum bulb, but that gets expensive.