I never owned a 9000ED, so I can't comment on the real performance. But at least according to Nikon official web site, the Dmax for both 5000ED and 9000ED are 4.8, so they are the same. And both scanners can generate 16-bit RAW images.
By comparison, V ED's Dmax is 4.2, and generates 14-bit images. It does not have multi-scan capability of 5000ED, either. The scanning speed is also slower. So, the specs simply look inferior on V ED. However, after owning both V ED and 5000ED, I can testify that I can't perceive any quality differences between the two, at least from my eyes. Although I do perceive a faster speed on 5000ED, but it is still slow. It is as if on the highway with speed limit of 70mph, V ED is driving at 30mph, while 5000ED is at 40mph. Upgrading your PC and memory might be a better move to improve the speed! 😛