Hi there,
I would choose to use Joomla. As most of the setting you can do it in the admin cp. Yea, it has user friendly interface. It is of course easy to setup and configure. For stability, i think it is great too. Joomla fixes bugs and security loop hole pretty fast. For mambo, i don't use it because of it's interface. Actually it looks okay, it just that i don't like the feel of it.
Well that's just my suggestion.
Regards.