hps all the way, there is no comparison between the two, only use cfl's if you have severe height limitations, and by the way watt for watt cfl's put out more heat than an hps, its just that its spread out over a larger area thats why you can put the bulbs closer to the plants, this seems to be a theory i see countless times throughout the pot sites that cfl's run cooler, i mean its bunk, a hps puts around 55% of the energy used in to light and the rest is heat, a cfl puts around 30% of the power in to light and guess where the remaining 70% of energy goes?????thats right heat!!!!!!!!!!!!