The two applications seem to do almost the same thing (there are more items in kontrol-panel). Both show up in the application list as "Control Panel". This is quite confusing.
I've changed the .desktop entry in 2.1-5. You're right, they're doing pretty much the same thing, kontrol-panel was originally meant to replace control-panel, but some fools^H^H^H^H^Hpeople didn't like the idea of depending on Qt for a basic configuration tool.