Kubuntu isn’t better than Ubuntu, just different. Kubuntu is Ubuntu with the KDE desktop and infrastructure replacing the Gnome desktop and Gnome infrastructure. KDE originally stood for Kool Desktop Environment, but is now known by many as the K Desktop Environment. KDE is powerful, flexible, and it can be fun. I think that “Kool” still applies.
Kubuntu is better than Ubuntu (with Gnome) if you prefer a desktop environment with traditional menus, launch icons and a system tray at the bottom of the screen.