Right CRI increases as the Color Temperature increases. Why do you think that they call 5000-6500K full spectrum because it literally covers all spectrums. Which would mean it would render all colors. Thats why the CRI gets higher.
Dude i think you got me all wrong, Im not saying that you should ALWAYS aim for higher CRI, im just saying if you have two 2700K 42 Watt CFL's, one is 69% CRI and one is 85% CRI then go with the HIGHER CRI bulb.
In all reality you want to simulate nature inside your grow room and the color temperature of natural sunlight changes throughout the day. In the morning and at sunset, natural sunlight is in the 2,500 - 3000 degree K range. That is why the Grand Canyon and fall trees look so brilliant in morning and afternoon sun. Conversely, at high noon, normal sunlight is very near 6,000 degrees K .That is why evergreen trees and blue water look so good in brilliant full spectrum sunlight.
So in order to simulate that environment youll wan't to mix and match the spectrum's throughout the ENTIRE grow.