CRI is color rendition index. Basically means if you put a color sample under the light and look at it, how close will it appear in color to the same sample in sunlight. While nice for looking at your plants because it is based on human perception of color, it means nothing for the plants growth. Lumens and color temperature are much more meaningful as far as the plants are concerned. Lumens tells you the amount of light while the color temperature indicates spectrum balance.
Christian I wouldn't stress the spectrum too much, as long as you stick around the middle somewhere. Much more important is the amount of light.