I personally switched from NextCloud to Syncthing.
Syncthing:
is easier for me to maintain,
allows for the "server" to be behind NAT,
lets me have multiple "servers" at the same time (eg. something at home and a VPS)
lets me have certain "servers" set as untrusted, so all data on them is encrypted, while others can have it unencrypted for easier access
I put "server" in quotes, as Syncthing doesn't really have a server, all clients are equal peers.
On the other hand, NextCloud:
gives me a way to share files by link with others,
lets me browse files via a web interface,
mobile app lets me access files as I need them instead of having to synchronize everything.
I personally switched from NextCloud to Syncthing.
Syncthing:
On the other hand, NextCloud: