Interesting – for basically the same reason we made the inverse switch from Resilio to Nextcloud with a small startup team with <10 devs.
Nextcloud provides us custom shares, user groups, public shares, URLs, better local clients, compared to the Resilio performance. Resilio was especially bad on Linux (but worked remarkably well on my android with a large SD card). With Nextcloud I can even choose to use WebDAV only if I don't want to mess with clients.
I guess it depends on your workload. My Nextcloud was only for myself and my family, and we only used it for "files on the go".
Calendar/contacts is handled by iCloud (Apple household, it's a Danish thing...)
Notes are handled by whatever each person finds the easiest. My wife defaults to the iOS notes app, i switch between various clear text editors.
File synchronization on desktops/laptops is handled by Synology Drive, which syncs beautifully whenever the machine is connected to our LAN, either directly or through VPN.
The only problem i needed to solve was ad-hoc access to files on mobile devices, preferably without opening ports, and since VPN doesn't always work from other private networks (ip scope clash usually), i chose not to use Synology tools for this. Besides, Synology Drive doesn't support selective sync, and while documents probably wouldn't be a problem, synchronizing gigabytes of books to my phone isn't really an option :)
Resilio on Linux does have a nasty habit of doing disk IO all the time, a habit that syncthing doesn't have. When i look at running processes, Resilio on linux is constantly using 2-5% CPU.
Nextcloud provides us custom shares, user groups, public shares, URLs, better local clients, compared to the Resilio performance. Resilio was especially bad on Linux (but worked remarkably well on my android with a large SD card). With Nextcloud I can even choose to use WebDAV only if I don't want to mess with clients.