There is a case where using the extra license for the syslog server is beneficial, though.
Syslog traffic is UDP, so if you're monitoring a remote data center and the link between that center and the LEM goes down, syslog traffic sent in that time is lost. However, the LEM Agent caches data when it can't reach the LEM, so that data will wait until the link is restored and then back-fill the LEM database.
If you use a syslog server at the remote data center with the agent, then you'll get the syslog events cached and back-filled the same way.
Something to consider.