- a good terminal mode so I don't need to switch to another terminal, the builtin terminals either lag badly after 10K lines of input or render/behave strangely when used with ncurses programs
- pervasive, non-blocking async, this has gotten better over time especially with language servers being on separate processes, however many common tasks block usage completely, such as upgrading/installing packages
The reason I bring this up is because imagine those points but applied to your window manager. Since Emacs is not multi-threaded, if something inside Emacs freezes your whole X session will become in blocked case you run Exwm. For the same reason, it is a bit more responsive.