Ubuntu is based on Debian unstable, and if https://en.wikipedia.org/wiki/Ubuntu#Background https://en.wikipedia.org/wiki/Ubuntu#Background is still up to date,

Ubuntu is based on Debian unstable, and if https://en.wikipedia.org/wiki/Ubuntu#Background https://en.wikipedia.org/wiki/Ubuntu#Background is still up to date, they freeze packages from Debian unstable before releasing, which looks pretty similar to Debian Testing getting packages from Unstable that have not proved too buggy. So you basically have this ordering more or less in terms of stability and how dated the packages are: From older (and more tested) to newer (and less tested): Debian Stable | Ubuntu | Ubuntu devel <-> Debian Testing | Debian Unstable Ubuntu devel <-> Debian Testing meaning that their orders depend on their respective phases, e.g. Debian Testing will soon freeze (prior to the next stable release) so in that time Ubuntu devel will probably be more up-to-date by virtue of being based on unstable. The rest of the time there's automatic migration from Unstable to Testing provided no blocking bug is discovered, so I'd expect packages in Debian Testing to be more recent. Honestly I think the main differences are the default experience, but if you know which packages you want to use, Debian and Ubuntu should be pretty similar.