The difference is the protocol and how it is implemented. FolderSync uses a array of different libraries to handle transfer using the different protocols, and the all differ in implementation of course. The sync engine is the same though.
If you have problems with FTP always try legacy mode first, perhaps also without SSL (FTPS, FTPES) if possible, to see if the problem is connected to that.
Best regards
Anders Carlsen
Software Developer
If you like our apps, please give them a 5-star rating. Thanks. :-)
Tacit Dynamics