How does Dell EMC Unity XT differ from Dell EMC UnityVSA?

Unity XT supports FAST VP onlyUnityVSA supports FAST VP and FAST Cache

Unity XT supports host I/O limits and monitoring and reportingUnityVSA supports monitoring and reporting only

UnityXT supports FAST VP and FAST Cache.UnityVSA supports FAST VP only

UnityXT supports monitoring and reporting onlyUnityVSA supports host I/O limits and monitoring and reporting