Hi Ajay,
these two tools are trully different serving different purpose. Sonar in NPM helps you discover and add devices into monitoring of NPM and other Orion (web) based products... Engineer's Toolset Sonar does this for monitoring in Toolset only.
So depending on what you are trying to achieve, you may want to run Sonar in NPM or both.
Let me know should you need some intro into Toolset and I will be happy to help (also via GoToMeeting or a call if you want..)
Regards
Peter