LED vs Florescent is mostly about the human factor. Both can provide plenty of light for plants, both can provide reasonable spectrum.
LED's can have a lot more flexibility, such as varying colors, special effects (storms, etc.), fading in and out (most florescents cannot dim, but you can turn some tubes off if more than one). LED's are generally much smaller, much more efficent, and last (nearly) forever - florescent need to be changed 1-2 times a year to keep their spectrum usable (you can't just run them until they burn out without lost growth potential). Because they are more efficient, they do not add as much heat to the tank (especially helpful if your room temperature is near/above your desired tank temperature).
LED's are more expensive, generally, though coming down in price all the time.
