Mambo used to be the no. 1 CMS when it came to simplicity. Unforunately there was a "battle" about who should be in charge of the development of the CMS between the developers of Mambo and the administrative team of the company Miro that held the copyrights. It was also an attempt from Miros's side to find a way to start charging for Mambo. This battle ended with ALL developers leaving Mambo, and they took the source code with them and formed www.Joomla.org For all of us that used Mambo for our sites, it was a few months being uncertain what to choose. Mambo or Joomla. I made my own decition to go for Joomla after I saw how the management of Miro tried to use force to keep people quiet at the forums of Mambo about what really happened. Many that tried to speak up were actually banned permanently from their boards. Happily the spirit of Mambo and the tight community lives on with the new name Joomla (Joomla has the same codebase as Mambo). What is really sad about the "incident" is that the company Miro tried to actually charge for the thousands of voulenter hours put into making the CMS as good as it was. None of the people that actually made it ever got payed for their work - and the company even tried to charge THEM for having the right to work for free.. So, I would suggest having a good look at the forums and do some reseach about both Mambo and Joomla before you make a descision what to go for.
I have used Drupal for quite some time, and I like it. Recently, I started using Joomla, the interface looks excellent. Not bad.
If you ask like that, I think every CMS has it own advantages and disadvantages. Prefer what you feel the most suitable for you.
Joomla was the result for me after installing and playing with 7 different CMS's I wrote a short article on it on my webpage. It is easy, it is actively being developed by a full time team and the community is very helpful and friendly. Plus it is easy to use and to add extensions to.