As CVBruce wrote, -r is already in -a. Even -z will not help even for a remote system for already compressed files as most music and video will be.

FAT partitions can cause a number of problems for rsync. Timezone is one, but you also might nead a time window, because the time resolution in the FAT file system may not be the same as the other system.

Also, the ownership may be making the files appear as different.

From the man page:
--modify-window=NUM compare mod-times with reduced accuracy