* Stability: I consider Debian testing/unstable more stable than Ubuntu stable (Try updating an ubuntu with lots of package installed).
* Privacy: Debian is more concerned about User's privacy then Ubuntu. If your iceweasel (now firefox) automatically connects to internet to load some data against your wish, you can consider this as a bug in Debian (and several other examples).
* Community support: You get community support from both Ubuntu and Debian communities.
* Truely free software 0: No non-free software by default. No binary blobs. But you may choose to have, if you wish to.
* Truely free software 1: In Debian, if you solely install packages from 'main' repo, you can safely use it, even in commercial setup. But in ubuntu, there can be packages that may commercially have several restrictions (and those repos are enabled by default).
Everything is from upstream: GNOME, wayland, flatpak ...