i also use a dual spectrum bulb witch is a 1000 watt bulb ...
its 60% red and 40% blue ...
they say that these kinds of bulbs are better then just all red or all blue spectrum ...
i also have a 400 watt hps bulb ...
the dual arc bulb is way far supperior ...but u must put into account that the 1000 watt bulb has 600 more watts then the 400 so its not a fair compairison ...
they say that plants will strecth a bit more under a hps rather then a dual arc or a bulb with some blue in it ...
um, from what Ive understood, your getting half the amount of light from a duel arc bulb at any particular time. Since your bulb is dedicated half and half and not full to veg and full to flower. You will get your best lighting going with an MH bulb and an HPS bulb.
In theory it's correct to have MH for Veg and HPS for flower but in practice I get alot better results both in veg and flower just using a duel spec! Won't go back now!