Myself I prefer to use 3-400w lights for a couple of reasons.

1) I get an extra 200w of light

2) If I lose a light or ballast I still have 800w compared to "0" if I just had one 1000w lamp.

3) I can position the lamps so they are on top and to the sides of the plants.


I never compared a yield but I would guess with the right lamp positioning, it would give a greater yield due to the intensity of the light in the lower regions of the plant. :twocents: