18.04: Why both Xorg and Xwayland?
See this Ubuntu Insights post:
We have decided that we will ship Xorg by default, and that Wayland will be an optional session available from the login screen.
Why opt for Xorg by default? There are three main reasons:
- Screen sharing in software like WebRTC services, Google Hangouts, Skype, etc works well under Xorg.
- Remote Desktop control for example RDP & VNC works well under Xorg.
- Recoverability from Shell crashes is less dramatic under Xorg.
For an LTS release, it's not practical to ship Wayland as the default when too much still relies on X11 features.