It is safe to say that Debian and Ubuntu are both two essential and dominant Linux distros with a set of different features and tools. Debian is more stable than Ubuntu, that is because Ubuntu uses or adds more cutting edge features, that results in more bugs and crashes.
Debian vs Ubuntu system performance, the clear winner in this study is Debian as it comes with a bare minimum feature and has astable base. Debian demands fewer resources and runs smoothly on a wide range of devices (old or new machines).
In Ubuntu, the added features and prepacked customizations sometimes affect the overall performance. Ubuntu provides the latest features that needs more power. So Ubuntu Linux is more suitable for modern computing devices.