Both lights are energy efficient light sources that are much more efficient than the incandescent bulbs they replace. Here is a small list of the differences between CFLs and LEDs: a. CFLs are the spiral tube like bulbs. They are really mini fluorescent bulbs with self contained ballasts. They contain a small amount of mercury. LED bulbs are the new style looking bulbs with heat sinks and round mini globes. They do not contain mercury, b. You can replace a 22W CFL bulb with a 11W LED bulb, c. LED bulbs are instant on, instant off. CFLs take 30 seconds to 1 minute to warm up after they are turned on, d. LED bulbs are not affected by turning them off and on. CFL bulbs are, as this will reduce their life.