They are somewhat similar but going from A to B:
Synchronise B = A always (a sort of one-way Mirror)
Backup B might have more files than A after the backup (not deleting files straight away if set or versioning)
If I am correct in thinking that what you are trying to achieve is:
You download the database to PC 1 make some alterations then use Syncback to upload it back to Dropbox, then maybe do something similar on PC 2.
If that's the case then you should use Synchronise PC n to Dropbox
Synchronise B = A always (a sort of one-way Mirror)
Backup B might have more files than A after the backup (not deleting files straight away if set or versioning)
If I am correct in thinking that what you are trying to achieve is:
You download the database to PC 1 make some alterations then use Syncback to upload it back to Dropbox, then maybe do something similar on PC 2.
If that's the case then you should use Synchronise PC n to Dropbox