WSA is DIFFERENT. It was designed to be compatible with other AV solutions. WSA and other AVs can actually work together just fine.
Many of the users here on the Community, however, tend to feel that there is no need to use more than one AV solution in an active state at the same time. That being said, there are many who DO use WSA along with another solution.
So IMO I would uninstall your other Anti Virus and install Webroot.