From What Aspects Can LED Grow Lights Be Evaluated?

The range and ratio of different wavelengths/colors of light, your light intensity and your light efficiency, these are the most important when grading LED lights.

The only real way to measure the wavelength range and the true intensity of light is not in watts per square foot or lumens as most people think, but through:

PAR, PPFD, and to a lesser extent, PPFD/Watt ratio. What is PAR and why is it important?

PAR stands for "photosynthetically active radiation".

Although some LED lamp manufacturers (incorrectly) use the term PAR when talking about light intensity, PAR is not a way of measuring light intensity.

PAR is the range of light of all different wavelengths/colors used by plants for photosynthesis.

Or your plants are growing in the best way, and your LED lights should have all the different wavelengths/colors of light that make up the PAR. But it is particularly important:

Blue wavelength (for vegetative growth), and; orange/red wavelength (for flowering process).

Fortunately, most LED manufacturers are aware of PAR and design their lamps in such a way that there are most light wavelengths/colors that fall within the PAR range.