Have now been using Syncthing for 2 weeks, My experience on the key differences between Syncthing and Dropbox, classified by importance (to me).
Huge Matters
1… Syncthing is much faster on local Lan transfers.
Dropbox does allow for local lan transfers (port 17500) but as the data also has to go to the cloud servers anyway, this is a limiting factor.
So it becomes practical with Syncthing to sync much larger files (1Gb, 2Gb)
which you cannot do with Dropbox because getting these to the cloud would take too long.
2… Syncthing can sync different folders with different devices.
So there are some items I share only with other computers,
other items I share with mobile Android devices.
Dropbox shares everything with every device on your Dropbox account.
Big Matters
3… Syncthing can sync multiple folders instead of just one Dropbox folder.
So Syncthing can fit in with my file system so the things I sync are better organized.
4… (Linux only)
Syncthing installs / updates from the repos - very convenient.
With Dropbox I have to manually download/unpack/install
and (as I want to control the update schedule) manually update.
5… Syncthing has transparency - I can see what is happening.
This is important for me, but not for everybody.
6… Syncthing does not sync to the cloud, Dropbox must.
For me, I prefer this, but some people would prefer the cloud backup.
Small Matters
7… Dropbox requires 2 apps to sync on Android: Dropbox + (paid) DropsyncPro.
Syncthing only requires one.
8… Dropbox allows you to share files with someone by just giving them a link,
in Syncthing of course this is not possible.
For me, I separate syncing from cloud backup,
and so use my cloud backup service for that giving people a link to files.
Really Annoying Matters
9… Dropbox documentation uses phrases like:
“Want more detail? Here’s the scoop:…”
When I read this kind of garbage, I want to smack the person who wrote it,
and flush his computer down the toilet.
(in Hitchhiker’s Guide, these kind of people were all put in a ‘special’ spaceship
and sent on a very very long journey).
Syncthing documentation is not perfect but it does not insult me with marketing garbage.
Summary
So now I have ‘dropped’ Dropbox.
Hope this is helpful to someone trying to determine if Syncthing is worth the effort of changeover.