12th August 2017
The Ubuntu project has this ridiculous idea that it "just works". This means the documentation is really bad so when something breaks you can't fix it. Compare Ubuntu's Wi-Fi documentation (400 words) to Debian's Wi-Fi documentation (1600 words). Ubuntu doesn't "just work" any more than any operating system, in fact in my experience it's very unreliable. When I'm using Ubuntu I honestly read the "Arch Linux" docs more often than the Ubuntu docs.
Ubuntu gives the users what they want. This means you get more up-to date software. This is very bad because it means the updates aren't tested thoroughly. Ubuntu desktop and Ubuntu server are based on Debian's "unstable" and "testing" branches respectively. Instead of the over 1-year of testing that Debian puts the software through Ubuntu does maybe 3 months of testing.
This is why Ubuntu is so ridiculously bad quality and unreliable. I've seen Ubuntu desktop become un-bootable after a regular update. I've seen enterprise Ubuntu servers go completely down due to "security updates" (happened yesterday at work). Just try using Ubuntu it won't take you long to find something that's broken.
Debian is made up of Free Software AKA Open Source software. This is software that's written in an ethical way, following the principles of sharing. However, Ubuntu seems to have little loyalty to software freedom and their software repositories advertise a mixture of Free and proprietary software all jumbled up together with no easy way to know which are Free or not.
Debian is suitable for almost every use-case so there's no reason to use Debian-derivatives such as Ubuntu. Or Debian-derivative-derivatives such as "Linux Mint". These are just commercial re-mashes that are so much worse than Debian.