PhatJay is right.

Another pro is that using multiple smaller CFLs they add more points of light. Which does help with getting them bushier as well as making up for their lack of penetration.

Also if you use the smaller watt ones like 26w or 42w you will have to bring them down closer to the plants. They put out much less heat than your MH but they can still burn the plants if they are too close or the ventilation is poor.