Impossible. Performance is highly dependant on the hardware used, among other factors in the environment. Because NBU is installed on typically your own hardware, it's impossible to predict the performance compared to a purpose built, dedicated appliance.
In almost all cases, a dedicated appliance will be faster by a large margin vs a NetBackup server with dedupe licensed in. Of course, no one will ever meet that performance metric unless they have the infrastructure to support it (e.g. 10GbE, 8GB FC, fast source servers, etc)