The way you phase that question, CFL's would probably be the way to go. But there is really more to it than that. Consider this:
1. How many watts of electricity does it take to get 10,000 lumens out of CFL's or HID's?
HID's = about 100 watts.
CFL's = about 150 watts.
So you are paying half, again, as much to power CFL's right from the get-go - THAT'S EVERY MONTH!
2. Most CFL grows (that I have seen photo's of) use really shitty reflector/hoods (or none at all), resulting in a massive loss of light - costing even more. More CFL's and even more over priced electricity to run them!
I have found that CFL's work very well in a "Micro-grow" situation, but anything bigger than about 1 square foot and HID's are really more economical, in the long run!
