Higher is better. If you go to any site that sells bulbs that shows CRI ratings you will find that the bigger name higher dollar bulbs have a higher CRI rating.The higher the CRI rating, the closer the light is to natural sunlight. A higher CRI rating means a broader more full, more complete, more natural spectrum of light for your plants.
PlusRite 1000-watt HPS. Price $27.12 each. CRI. 22
Eye Lighting 1000-watt HPS Price $76.81 each. CRI 26
Prices used from 1000 bulbs site .. the same bulbs may be less or more expensive elsewhere. The site was used because some sites that sell bulbs do not bother to mention CRI ratings.
Also .. they do differ if you are talking about MH or HPS bulbs or ones with dual filaments.