Someone was talking about the CRI before, its not important for grow lights, as CRI refers to how well the light source maintains the original colour of the things that its lighting. So if your plant looks really green or slightly purple under the light, this makes no difference, to how much light the plants absorbing, focus on the colour of the actual light, do you get red or blue at the most delicious wavelength or not.
I'm biased, but hey here goes, forget the HID, HPMH, HPS etc go for LEDs, sit down with a calculator and figure out how much money you will save on the electricity, it will blow you away, also you'll have environmentally friendly weed, Happy days
