To make it short:
Now I use (again) SyncBackFree
Before (up to 2017-02-01) I used FreeFileSync
o) good overview on the changes before the sync
o) versioning (maybe the greatest advantage)
o) portable (now only available in donation version)
o) tries to install additional software (not in donation version),
sometimes Avira Antivirus blocked a downloaded version
o) donation version *costs* € 5,00 per month (it is not a one-time donation)
I think € 10,00 per year would be enough.
FreeFileSync worked excellently, but the above mentioned disadvantages let me switch back to SyncBackFree.