Kubuntu versus Ubuntu 9.10
The title is rather misleading as Kubuntu runs on Ubuntu and there’s no way to make such a comparison. However, even the award winning Ubuntu operating system doesn't promise 18 months of free security updates, and a biannual release cycle. This K Desktop Environment based application is even available in form of freely distributed CDs for PC, from https://shipit.kubuntu.org.
People prefer Ubuntu as the choice of operating system despite the presence of powerful ones like Suse, due to the sheer fact that Ubuntu is lighter, boots faster and works much better and quicker than other Linux flavours.
You can read user reviews about Kubuntu and find more Kubuntu versus Ubuntu analysis here:
Changing Konqueror Profile back to default KDE profiles?
If you wish to move from Konqueror to default KDE profiles, you just need to type in:
sudo rm -r /usr/share/kubuntu-default-settings/kde-profile/default/share/apps/konqueror
sudo cp /usr/share/apps/konqueror/konqueror-orig.rc /usr/share/apps/konqueror/konqueror.rc
You can also use the command: sudo rm -r /usr/share/kubuntu-default-settings/kde-profile/default/share/mimelnk/application/ - to enable Konqueror to open tar and zip files
RAM and Memory Requirements
As per beta testing results and experience of current users, Ubuntu requires a little higher RAM to work well (with Gnome running), while Kubuntu needs relatively lesser RAM to work satisfactorily.
Graphical User Interface (GUI)
Ubuntu and Kubuntu have different GUIs, as Ubuntu uses Gnome and Kubuntu uses KDE. As a matter of fact, the underlying implementation of most of the *Buntu OS is the same, but the GUI varies from one distribution to other. You can learn more about various types of Linux distributions here.
Even when you consider other desktop environments like Xubuntu, the GUI is the only major variation, while most of the operating system doesn't change.