Why OpenSUSE? Like the Shamwow guy says, "You know the Germans always make good stuff." Actually my (now old) certification is in OpenSUSE, but that's because I don't like RedHat and I didn't have to take a class for the Novell certification, just self-study so it was easier. That being said, OpenSUSE is really solid, conforms to the Linux standards (so knowledge pretty much transfers), and I like KDE. I used Gentoo for a while, and probably will again at some point on some box. So, historical reasons
Why OpenSUSE?