At work we were asked via email what we liked about Debian. This is my response:
In Gentoo, I have an incredible amount of control over my packaging. In Gentoo I can choose to have certain features included or omitted in a package without much effort. This reduces software bloat and reduces the potential points of failure/insecurity in a given piece of software. Package dependencies are usually handled very well and it’s easy to find and get information about packages. In Gentoo it’s trivial to install an unstable version of a specific package and restrict any package to certain versions (or to accept an unstable package up to a certain version). Gentoo cleanly separates configs for services and service startup. Gentoo is an awesome system to get things just the way you like them.
The problem with this level of detail and configurability is the need to actually manage it. Because Gentoo as an OS doesn’t have a version, sometimes you’ll perform regular updates and break a service: this is normally handled by having a new OS version, forcing you to reconfigure things intentionally. Debian makes intelligent decisions about when a new, incompatible version should be made available simply as a new package version or as part of the next OS version. Gentoo’s incredible detail and flexibility means that you have to consider the details and possibilities for each package that you install. While Debian doesn’t tend to offer you choices within a specific package it does make intelligent decisions as to when to split something into multiple packages, when certain things should be defaults, and when certain things should go through a post-config dialog. Package updates in Gentoo are like russian roulette while in Debian they’re just routine package updates.
Gentoo tries to make absolutely no assumptions about what you want. Debian assumes that you want a stable, easy to configure and maintain linux system and acts accordingly.