ISE is the preferred identity integration source for FMC. When you have ISE (plus Active Directory) integrated, the firewall(s) and the management center have additional information to use for both policy enforcement and visibility. Specifically, IP addresses are matched with end users (the ISE integration) and the users' AD groups are known. So you can see end user information in things like connection events as well as use user or group information in your access control policies.
