That requires you to have always on, central server running and stroing things. Devices running syncthing are run as equals. (or they can be configured not to be)

One cool feature is also encrypted syncing where some nodes dont even have the key (ie VPS syncs but doesnt know what it syncs, and only your devices have the key)

NextCloud is great but like any webapp suffers from bloatedness and cryptic errors. If you've ever tried uploading terabytes with the web client, you know what i'm talking about.

Also, performance (read bandwidth usage) isn't all that great with NextCloud. PHP-FPM was more designed for concurrent execution of multiple stateless requests server-side (PHP) than for sending raw bytes as soon as possible to the disk.

From my experience, the nextcloud android app autosync features are unreliable while I never had this problem on syncthing.

Does it have a command line client?

It’s indexing speed is slow