Syncthing is a file syncing service. This is a file transfer service.

Dashbeam is more for occasional transfers, it seems. You want to send me something right now, you use Dashbeam.

Syncthing (which is great and I use) is more for background sync between devices. I use it to sync and backup my important documents automagically between my devices.

So, Syncthing is definitely great and you should use it, if it fits your usecase. I don't know about Dashbeam (in the sense of whether it actually works or not), but the usecase seems a little different.

I haven't used this but from their website / description it looks like they are more of a on-demand file transfer service, e.g. they are comparing themselves to Magic Wormhole, PairDrop, LocalSend, etc.

Syncthing has its roots in being used for automatic file/folder synchronization, that's its strength. But sure, you could set it up for a one-time file transfer too if the other person is willing to set up Syncthing on their end.

DashBeam does seem to be able to do transfers via web browser, that could be an advantage if the person you want to transfer something to/from does not want to install anything extra on their device.. but I don't know how well any of that works in practice.

Good question, the actual idea for both is a great one and not something I was aware of.

Looking up an actual comparison, I can't find one yet since this is so new, but perhaps that's part of the plus, since new might mean better transfer process and speed, security, etc. Old isn't always a bad thing, but some commentary I ran across looking for alternatives to Syncthing was because it had limitations they ran into due to it being designed for specific needs and not general purpose?