Well, In my opinion CGC gradings have only a cursory relationship to the eye appeal of a book. For example, I have been looking for a high grade 181 for some time. The majority of 9.8 181's have various spine stressses/breaks which render them out of the running for me, still more have registraton issues. The 9.9, while free of spine defects and registration issues has a blunt upper right corner which also puts it out of the running for me. I have seen several 9.6's that would get my nod before almost all 9.8 scans I have seen as well as the 9.9.
My 2 cents, FWIW.