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I want to spend a little time praising Debian. When it comes to compliance with the FHS / LSB / SELinux I've found debian to be by far the best. Maybe that's changed now but the redhat + arch based distros seem to be patchy at best, and I assume Gentoo would be fairly bad (a lot of tools ignore LSB compliance by default compiling, meaning the package managers have to do the hard yards ensuring compliance. Since Gentoo would likely do default compiles, this would mean Gentoo would violate FHS / LSB standards a lot).
Debian might split packages into teeny tiny chunks which certain groups (Ruby) might not like, but as a user it gives me a lot of flexibility out of the box. Add to the fact that Debian also supports BSD kernels and HURD, Debian is bigger than "Linux" and makes a great distro, especially as a "base" for other distros (which is why a lot of distros fork off it).
The package management is also second to none, even after all these years. Despite under the hood changes, apt-get hasn't changed from a user perspective in around 20 years. All this "app store" stuff that's the fashion today has been available to Debian users for a very long time. While most distros might be close to parity for package management now, apt / dpkg is still forwards looking enough to be able to take more steps towards modernisation.
It's also the best free-as-in-freedom distro out there, despite what the GNU guys say. Using it is like a big rubber stamp saying that there are a bunch of benevolent folk out there looking after you, your data, your privacy, etc.
This is why I always choose Debian.