LED curing lights (light-emitting diode) are made specifically for curing polishes formulated for the LED technology. It typically takes 30 seconds to cure. The LED curing lights are in the same light wavelength spectrum as UV therefore it is a UV LED curing light. LED lights are the same type of lights found in Christmas lights.
UV curing lights, the typical type of light found for these machines are fluorescence & incandescence. The type of light is still in the same light wavelength spectrum, UV. These lights can cure all types of polishes and takes typically two minutes.
Both of these types of lights are not any safer than the other. BOTH of these lights are safe because there is not enough power output to cause any significant skin damage. Researchers found these lights are 11-46 times less likely to develop skin cancer when compared to natural sun light. More info/source can be found on the blog below by clicking on the heading.