The total luminous flux or the entire light-output is showed in lumen.This size is the only comparison measurement to compare better to worse light sources. If you asks for the energy efficiency, then the ratio of lumens per watt is important. Look for the specified Data of the LED module, not only to the specified LED which is used. The light efficiency of an LED module can be greatly reduced, because of lenses, reflectors or inefficient LED drivers. The candela value is only important when you speak about the brightness in the center of the emitted light beam and not about the efficient lighting of a complete area. An example of this is a punctual highlighting of goods in supermarkets.