There is no benefit if you enable conditional DNS. It is required in your environment or not. If it is not required and DNS resolution with the 3 ISP DNS works great - don't touch it.
It is used to use different name servers for specific domains, e.g. if you need internal name servers for internal name resolution and your ISPs name servers for external resolution. Since it adds more complexity to the environment only enable it if it is really required for operation.
Many thanks Andre.