Assuming the recipient has none of the files you are sending, combining many small files into a tar can increase performance since the disk reads will be more sequential than random. Then when you perform the rsync using compress (if the tar file is compressible) means you'll save some bandwidth. You still need to untar the files on the other end though. So, end to end, whether you'll save time is specific to your situation and up for debate.
https://unix.stackexchange.com/questions/30953/tar-rsync-unt...
https://stackoverflow.com/questions/20587648/can-i-rsync-a-t...