The NAS R-3 versions are built from the DSS (Data Storage Server) engine, this means that one update will be for all updates. In NAS XSR versions - there are separate versions and separate updates. With these capabilities updates are significantly improved. But if your NAS XSR version is working properly with using the IDE DOM then why change? Remember the NAS R-3 versions are on a USB DOM so there is a physical difference. You can review the NAS R-3 by downloading the DSS Demo-CD and use the NAS portion of DSS to experience the NAS R-3.