Full Online Backup VS. Online Synchronization

I'm using the Cronus 2012 TrueImage home. I am also using online backup. I have chosen to use the online backup option instead of the synchronization back up to the online service.

I'm wondering how these two different options operate. I have 230 GB to upload and him wondering once everything is uploaded online if I were to then back up again would it attempt to re-upload the 230 GB. If I were to use the synchronize method would it simply replace the old files with the new files thereby making a quicker backup.

Thank you for all the help you are willing to give.