I've heard some recommendations that bulbs using different spectrums of light should be used to achieve great results in a planted tank (e.g. to use 2x 6500K and 2x 10000K) while i've heard others say that as long as you use all bulbs within the 6000K to 8000K range (so 10000K bulbs are actually not very useful), your plants will make maximum use of the lights.

Based on your experiences, which would be a better path to follow?