CRI is how accurately the light achieves its rated spectrum. The higher the better, but as you approach 80+ the difference is pretty negligible for how much extra it tends to cost to get 90 vs 80. I believe a lot of the leds high end grow lights go with are 80CRI but ive seen a fee that claim 90+ for a crazy price increase. Heck some of the lights ive seen that claim 90CRI cost so much that i could buy 2x the amount if 80CRI lighting. But essentially yes, if you have 2 of the same lights, 90CRI will grow plants very slightly better than 80CRI though i wouldnt spend the extra money for it.