Area of a grow depends on it also. Cause CFL doesnt have the coverage. Even though they can provide up to 5x or more the proper feeding red spectrum. They just dont have the muscle to power bigger areas.
4sq and under. CFLs can do a superior job. And thats according to guys like Ed Rosenthal. I know some dont care for him, But if Sensi likes him enough to name a strain after him, then his word is good enough for me.