There are two main drivers for this decision: first, as you already mentioned, systemd-nspawn requires root privileges when creating a container instance. With

There are two main drivers for this decision: first, as you already mentioned, systemd-nspawn requires root privileges when creating a container instance. With schroot this is something I don't really have to care about. The other important reason is that I try to keep the slingring codebase as small as possible. At the moment, I maintain this project alone and I want to keep it manageable in the long term. I actually started Slingring using nspawn containers, but I found that handling things like providing the user/group nss databases inside the container had to be done by myself, while schroot includes that functionality. On the other hand, I simply do not need the greater flexibility that is provided by nspawn-containers at the moment. This could change in the future. Therefore, the coupling with schroot inside slingring is kept to a minimum and I might switch to nspawn whenever it might suite my requirements better.