FRS is a legacy (invented in Windows 2000 along with AD) SYSVOL replication service, while DFSR is a newer. Main difference is that legacy FRS replicates entire changed files, while DFSR replicates only changed bits, which generally improves replication strategy and minimizes replication traffic.
However, you need to make sure that you are still using FRS. For example, domains created by Windows Server 2008 or newer use DFSR by default. Run:
dfsrmig /getmigrationstate
if status is Eliminated
, then you already use DFSR and no actions required.