I think the benefit of resolved is that you run a local DNS server and you can do a lot of additional things with that (I think for example avahi hooks into that so you can interact with other machines in your network by their hostname etc.) Also afaik NetworkManager by default can't do split DNS for example which is nice for VPN.

I mostly use resolved on my work machine (Ubuntu) and I do use it's plot DNS feature

Until now I was pretty sure it's only useful if you run systemd-networkd since you would disable NetworkManager.
Benefits would be a more lean network setup with less memory usage and dependencies.
Can't speak on how Ubuntu does things