[smokinreefer]

with LEDs, I think its a mixture of colors that are needed...
each led omits a different color
and newer fixtures are now including a wider variety of colors to help simulate full spectrum lighting

I believe we are mostly past the days of LED users just using blue and white.

if you have experience with MH, its like back in the day the question was;
6500k vs 10,000k vs 20,000k etc
and for the most part it was just aesthetics
MH was a more well rounded light source, in that a 20,000k bulb wasn't just a blue bulb, it provided a variety of different spectrums, but was "bluer" in appearance.

so, with LED, I'd use both blue and white and some of whatever else is included in whichever set up you choose or build!