One big advantage is user services/daemons. I've recently converted most everything I used to start in .xsession to systemd user services and it worked very wel

One big advantage is user services/daemons. I've recently converted most everything I used to start in .xsession to systemd user services and it worked very well. I did it mostly as a way to learn about systemd, but I'm happy with the results and it makes it much easier to diagnose issues and maintain a consistent environment.