I would suggest Debian because this question breaks down into two things:
1 - What is a really good, stable, easy-to-use Distro?
Answer: Debian, for one, because it's established, reliable, and dpkg/apt-get is super duper.
2 - How does a user learn about Linux from a distro?
Answer (in my opinion): by installing a base, command-line system and then building it up into the full system of his/her choice. By doing this, you introduce the user to the shell, which is criticial to *learning* Linux. A nice, fancy desktop is useful for *using* Linux but the process of, say, installing xwindows, installing XFCE, uninstalling XFCE, installing GNOME, uninstalling GNOME, and then finally deciding on KDE (for example) teaches the user something about the OS and how to make it useful for his/her purposes. That applies to individual packages, too. "Want to browse the web? Do an internet search for 'Linux web browsers' and apt-get your way to some testing." This gives the user an understanding of how the pieces fit together and it provides the skills necessary to make changes in the future.
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I would suggest Debian because this question breaks down into two things:
1 - What is a really good, stable, easy-to-use Distro?
Answer: Debian, for one, because it's established, reliable, and dpkg/apt-get is super duper.
2 - How does a user learn about Linux from a distro?
Answer (in my opinion): by installing a base, command-line system and then building it up into the full system of his/her choice. By doing this, you introduce the user to the shell, which is criticial to *learning* Linux. A nice, fancy desktop is useful for *using* Linux but the process of, say, installing xwindows, installing XFCE, uninstalling XFCE, installing GNOME, uninstalling GNOME, and then finally deciding on KDE (for example) teaches the user something about the OS and how to make it useful for his/her purposes. That applies to individual packages, too. "Want to browse the web? Do an internet search for 'Linux web browsers' and apt-get your way to some testing." This gives the user an understanding of how the pieces fit together and it provides the skills necessary to make changes in the future.