Sorry to revive an old topic..
I am a huge fan of SyncThing. I use Raspberry Pi2 to watch tv with OSMC/Kodi on it. But it also runs SyncThing and the attached HDD is basically my life with all photo albums. I have the same setup at my parents and inlaws for them to watch tv and store photos and other important data.
Syncthing keeps those RPi's in sync, allowing a backup on 3 different locations.
Smartphones sync photo albums on the phone to these RPi's. It all works extremely fast and smooth.
But I have to use SFTP to get files/pictures from those devices. It's a bit annoying and especially when I need to search for specific photos in albums it can be a pain.
Now I am considering installing Spydio or OwnCloud or _h5ai. Purely for their webinterfaces or in the case of Owncloud their mobile apps. I wonder though which one is the most lightweight since it will run on an RPi2. Would love to hear what others are using.