Hello Andrea,
I didn't see any publicly available, but if you told us do you want to compare with NX9600 or NX9610 we can sort it out in details I believe.
Main difference is, that VX9000 (and NX9600) are meant for centrallized deployments, so the controller is just for management plane, and all the rest is done locally at each site by so-called RFDM (RF Domain Manager), either one of the APs or an on-site controller, depending on scale. This also means, tunneling on these appliances is limited and no official support for tunneled (bridged at controller) WLANs compared to other appliances. VX9000 scales to 25,600 APs, NX to 10,240. There are also smaller differences between them.
NX9610 is the most capable as it gives you not only 10K AP scalability but also dataplane for tunneling.
NX7500 and NX5500 also have smaller scalability and some capabilities limited compared to NX96XX.
Hope that helps,
Tomasz