I hated Ubuntu, I've always been reccomended to use Red Hat. Ubuntu (not Kubuntu) isn't exactly a great OS, though it's very clean and effective.
Why would you define Ubuntu as "not exactly a great OS"? There is no different between Ubuntu and KUbuntu outside of the windows environment that is used. Since distributions are all pretty much the same, it really comes down to stability, security, support, and their package management system.
Problem with Fedora/Red Hat is it uses RPM (Red Hat Package Management). If you need/want to use software that your distribution doesn't support for you version, A.) you're forced to upgrade to a supported version, or B.) compile from source. When you want to upgrade to the next version, your force to boot from the install Disc.
In (K)Ubuntu/Debian/Gentoo, have much better package management systems. You download, install, and uninstall all from the command line. If a dependency is need, then it is download. Upgrading from one version to the next is just a command line away, and you never need to reboot unless you change out kernels.
The only times I would ever recommend Fedora/Red Hat over Ubuntu is if they have a slow internet connection, or possibly in a business setting. Otherwise, Red Hat just isn't flexible enough.