it depends on what kind of tubes you use. the best tubes for growing are t5ho (high output). they all make different claims and t5 is supposed to be brighter. i have used a simple guage light meter to measure both and it appeared to me that the light from the cfl was stronger. there are obviously a lot of factors in the comparison such as what watt cfl is being compared to what watt tube, and the fact that cfls concentrate all the light in a smaller space and tubes take that same light and spread it out. i have used both, and i prefer the t5 for the simple fact that they are easier to move (mine were internally ballasted complete with reflector) and they can more easily cover a larger space. they are not very good for flowering on their own but they are awesome for vegging. the main difference though is the price tag. 50 bucks will get you WAY more watts of cfl than t5 will, and if arranged properly will do just as good a job.