Synching is currently the fastest and lightest you will find, but the concept is different from Seafile or Nextcloud. With Synching there is no central server, you have resources (folders) shared between nodes on a peer-to-peer basis. This has several advantages, the most obvious one is that if a node goes down the rest continues working, but also that if a file is available in two or more nodes when a new node enters it will download that file from all the nodes in which it is available. As a disadvantage we could say that there is no web server where to see the shared files, so you will not be able to enter a URL with username and password and browse the files and upload or download. You will not be able to share files with third parties through a URL either.
Excuse me, but on what authority do you say it doesn’t suck? The comparison in the readme seems to be written by a resentful kid.