Selfhosted

I'm not PC but, one benefit of using a central server for syncthing is an always on backup that doesn't require another client device to be on, it also allows for easier creation of new shares.

For example, with syncthing you can set the "servers" client device to auto approve/accept any shares that are to trusted devices, then when you get a new device, instead of needing to add that device to every device you share on the syncthing network, you only need to add that device to the server and then you can have your other clients connect to the servers share instead of device to device. It's easier. You can also configure the shares on the server to use encryption by default too, since you don't really ever need to actually see the files on the server since it's basically a install and forget style client.

As an example of what I mean:

I have 10 different devices that run syncthing, 9 clients and a "server" client. these clients are not always on at the same time, and as such when I change a file, the files can become desynced and cause issues with conflicts. By having a centralized server, as long as the server is on(it always is) and client itself is online, it's going to always sync. I don't need to worry about file conflicts between my clients as the server should always have the newest file.

Then for example say my phone died. Instead of needing to readd every seperate client that the phone needs to share with to the new device, I only need to add the phone as a trusted source on the "server" client via the webui -> click share to that device on every share the phone needs, and then remap the shares to the proper directories on the mobile device. this is vs having to add every device to the phone, and the phone to every device it needs access to ontop of reconfiguring all the shares. It's simpler, but fair warning does cause a single point of failure if the server goes offline.