Isn't that mainly related to the UI and the packages installed by default (I haven't used ubuntu in like 5 years, but back then it felt just like debian with mo

Isn't that mainly related to the UI and the packages installed by default (I haven't used ubuntu in like 5 years, but back then it felt just like debian with more stuff installed by default). If Valve makes a complete custom environment for steam OS built around big picture will they really benefit more from using ubuntu versus debian, fedora or any other distro?