BIG DIFFERENCE!!

HID=High Intensity Discharge

HID lights that are best for growing include Mercury Halide (MH) and High Pressure Sodium (HPS).

CFLs produce a lot less lumens than HIDs, hence why they require less watts, however this is also why you need A LOT more of them to create enough light output for the plants to grow. Plenty of ppl use CFLs and Fluoro tubes to grow plants however the yield and grow time is greatly affected. (i used CFLs and fertilizers and nutrients for my 1st grow and was unsatisfied so for my 2nd grow which is in the assembly process (check out my thread) I am aiming to use HID lights and completely organic means... afterall nature knows best, not artificial.)

The other downside to HIDs are they cost much more, produce much more heat and may be harder to find (atleast in the Ontario area I have found that if i want appropriate HIDs I have to go to a hydroponics store, Home Depot and the like are no good).

Hopefully this info was useful,
Best of luck with your grow,
froze