--compress This will compress the files in transit. But it takes time to compression and the uncompress on the other side. I think if you are going over the internet you should use this option but if you are on a fast LAN don't bother. --checksum As the man page says, this will use a checksum rather than the easily obtained file metadata (modify time, size). If takes time to compute the checksum. And it needs to be done on both sides -- take note if one computer is older. If you are rsyncing a folder of files where there are few changes then calculating the checksum will dominate the process. If you have big media files (eg graphics, video) this will take a very long time. My advice is to avoid this option normally. Use it when the metadata might be wrong or occasionally on your backup as an extra check. If you aren't going to use --checksum make sure you use --archive or --time which preserve the metadata. --exclude Obviously, if you can exclude unnecessary files from your transfer things will go faster. As far as I can tell it takes rsync negligible time to process this option.
Computer Tips - rsync: speed tradeoffs for some rsync options
Date: 2013aug19 Product: rsync Q. rsync: speed tradeoffs for some rsync options A.