I used Joomla until just about a week ago when I got fed up with it.
Joomla looks great, acts great, and is great.... until you spend enough time with it. As said above, Joomla formating (WYSIWYG-wise) is horrible. I used a different editor (the most popular one, JCE), it is slightly better, but is still horrible. I am often getting calls now, with clients trying to get the formatting to work. It takes me going to the code and cleaning it to get it to work.
Joomla outputs tables, which although I am anti-tables, I could deal with.
So, I got tired of it, and switched to Drupal. It takes slightly more work to create the templates (as in 10~15 minutes extra work) and the PHP you need to know to get what Joomla offers you through their tags (adding content to the page for instance) is not much, and is well documented in tutorials.
You need to make an info page for each drupal template (similar to Joomla), but after that, you can just use the following for the Drupal-equivilant of a module (mine is called header):
And this to add the content area:
It really isn't that massive of a learning curve. It takes a few hours to get used to it, then it is nice. So far I have had no issues with Drupal, but, as said above, I've only been using it for a week.
When the clients get ahold of it, I recommend using the permissions system in Drupal to limit what they see to only what they need, which makes it much less overwhelming.
You have to install the WYSIWYG editor yourself (I chose tinyMCE), but it is fairly simple (10~15 minutes of work with their instructions).
If you choose to use Drupal, go
here for the WYSIWYG editor. It is the one I used... Also, be sure to read their "how to build templates" tutorial. It is pretty good, though sometimes confusing, and it does explain the whole template building process.
Also, Drupal is FAR more flexible than Joomla, providing that you know PHP. If not, then I would say that it is close, but slightly-less flexible than Joomla.
I hope that helps.
If you have any questions, just ask.
MegaMan1311