CRI measures how close an object illuminated by a bulb looks compared to sunlight. Most good grow lights will not have a high CRI as plants don't need the green some other spectrums.

Mike

With your CFL's you're interested in the top and bottom of the color temperature range. You want to look for the "daylight" bulbs with the color temp of 6500K for promoting vegetative growth. At the opposite end you want the ones around 2300K for the redder light spectrum many plants need for flowering.

A mix of the two types is ideal for the widest variety of growing conditions.

CRI is a good measure of full spectrum, which generally is desirable (with a slight bump in the red). There are many color spectrums other than Green included in CRI.

Kenny, I'm not clear what type of light you are talking about. CFL? 4' fluorescent? CMH? PSMH?

26 watt CFL, 6500k I placed a couple in the middle to add to the 2, 40 watt T12. cool white 4100k. On each side is a 48 watt red/blue LED. Problem is that the 48 inch T12s have to be way high up cause of one big tomato plant (with fruit started).
The T12s came cheap, and I might in the future strip them out and use the reflector to mount many CFLs.
Kenny

Instead of "many CFLs" why not consider a few 100w CMH
(ceramic metal halide)? They are much more efficient than fluorescents, and still have most of the benefits of CFL.
You can use several, and still get crossover of fringe areas; and can mount them individually (like CFL) to accommodate plants of different heights.

Concerning CRI of CFLs, that can be misleading because fluorescents tend to have spiky spectrum; the troughs may still be counted toward the CRI.

CMH has a point source that can be reflected more easily and efficiently than fluorescents. Several points can be combined to get different angles/better distribution.

the high pressure metal halides are better than flourescents, but the best thing growing is the sunpulse pulse start bulbs,
used properly, i.e. with a high frequency ballast, they are the closest any light has come so far to matching the sun's electromagnetic radiation profile. visible, near infra-red, and uv out to the nearer wavelengths of uvb are only part of the em profile. the closer you come to matching all those parts of the em continuum which penetrate the atmosphere, in the correct proportions, the better your plants will do.