I tested quite a lot of sync tools out there: Dropbox, G-Drive, Bittorrent Sync, ownCloud, plain Rsync,... You name it.
But to be true, I never really liked any tool that much: It never really *worked out* somehow: The Mobile Apps were bad, "Servers" did eat up too much performance, etc. etc.
And we don't want to forget these little itching problems with privacy - thinking about Dropbox, G-Drive and the now closed source Bittorrent Sync...
Well - enter Syncthing: https://syncthing.net/
In truth I can only say one thing: It works. It just, plainly, works for syncing data from your mobile devices to your swarm of servers or pcs.
So give it a shot :)!