Ubuntu’s popularity often makes it the default choice for new Linux users. But there are tons of other Linux operating systems that deserve your attention. As such, I’ve highlighted some Ubuntu alternatives so you can choose based on your needs and requirements—because conformity is boring.
Nothing. They’re mostly the same thing.
The Ubuntu version will sometimes print “ads” to your terminal :P.
For a prod server, I’d choose Debian over Ubuntu if I didn’t have paid support, because I’m not a fan of Canonical. If I needed paid support, I’d choose Ubuntu, because Debian is strictly a community distro. (That community happens to include major companies, like Google.)