HPS 600W VS HPS 1000W

We put 30# beneath a 600W HPS in 8"x 8" cups (8 liter each), per 1.25 square meter. (Sorry, don't know how to convert to feet). 0.88 ounce each, provided you have done everything alright should be possible. I guess the watt/efficiency discussion is a never ending one. There are unfortunately many and many more parameters which affect the harvest. We normally see 0.8 gramms (0.03 ounce) per watt at the better cultivator up to 1.2 gramms (0.042 ounce) for the experts. Much however also depends on the number of plants, sort of reflector you are applying (wide or narrow beam), age of the lamp, sort of the HPS lamp, reflection, etc. So the question still remains very difficult to answer. As to the efficiency of a 1000W in comparison to a 600W (or 2x600W), I think you're better off with 2 x 600W. The only difference is the Lm/Watt ratio, however, the 2 x 600W wil give you a better efficiency and make you more flexible, with of course the appropriate reflectors.