At the moment i have 2 drives plugged into the same machine running this command to sync them.

rsync -X -H -A -a -P /mnt/MyBook /mnt/offsite/MyBook/    

later this month ill be moving the /mnt/offsite/MyBook/ drive to my brothers house and want to 1) remove files no longer on the main drive from the offsite and move the new files over.

whats the best command to do this?