When I first decided to enter the world of blogging, I did so through Google's free Blogger platform. Ease of set-up and use, but a serious lack of flexibility led to me outgrowing it in short order.
My primary criteria for selecting a new package was the size of the ecosystem that would provide plug-ins and how-to's since I had so much to learn. I turned to Google Trends for this information, which is handy for a quick snapshot of how popular a search term is on the internet, but not a real indicator of the install base of the platforms.
Joomla in red, WordPress in blue, Blogger in Orange and Drupal in Green
Google Trends showed WordPress and Joomla were well ahead of Drupal, so I crossed the latter off my list. Since I had read that WordPress is easier to use than Joomla, the decision was made.
Fast forward some time and I began to develop a HTML5 Wiki in TikiWiki because WordPress web pages weren't really suitable for storing the interlinked pages of reference material that I was creating. Then the Mysterious Invisible WordPress CPU Bug reared it's ugly head and lead to me losing faith in both shared hosting and my host, so I decided to move to a Virtual Private Server at a different host, and during the move, switch to a more flexible content management package.
Based on previous research, Joomla was the new winner by default.
In order to help anyone else out there who is faced with a similar dilemma, I'm going to list a brief comparison of the features that both packages offer, in an effort to help you decide who your winner is.
Ease of use
If your aim is just to blog, then WordPress is for you. Joomla is a Content Management System so it will need to be bent into shape if you want ot use it for blogging, which means that you'll have to do some work after installing, such as add a commenting plugin and change how the front page is laid out and the way the system works to make it more blog like. Admittedly, there are a control panel settings for most options, but it's not a quick job unless you are already familiar with Joomla.
Ease of Administration
When it comes to protection against exploits and keeping the system up to date, WordPress is easier to maintain as it has built in functionality to identify and update both the application and plugins as new versions are released.
For sites that have many registered users and areas with differing levels of security, Joomla is the winner as it has a more robust and complete security model.
I've previously written about the hoops I had to jump through to get bandwidth usage as low as possible in WordPress. Imagine my surprise when I loaded Joomla and discovered that both caching and GZIP compressions were options in the administration panel. If you're going to have a lot of visitors, then every megabyte will count, so Joomla is the winner.
Then there's CPU usage. I've poked around in the code for both Joomla and WordPress, and I can confirm that Joomla has a much cleaner design. The biggest issue here is that WordPress will make repeated and unnecessary calls to fetch the same information from the database during a single page refresh. If your site is getting hit by a lot of visitors then this behaviour can get your account suspended. As with bandwidth consumption, Joomla is more efficient and is the winner.
Both platforms have a large and diverse collection of plugins and themes available, so both are winners. The difference is that Joomla is a more commercial platform and add-ons and themes are more likely to cost money. That's not to say that you'll need a fat wallet to use Joomla, rather, you simply won't always be able to get the add-on you want, unless you are willing to pay for it.
WordPress' built in add-on installer also makes it easier to find and install the extras you want, rather like a Linux package manager. Joomla on the other hand requires you to go to the vendor website, download the files and install them manually. WordPress is the winner here.
One other point I'd like to make about plug-ins is that the ones intended for WordPress seem simpler to use, mainly because they feature fewer options. This is both good, because it makes them easier and more intuitive to use, and bad, because it means they are less flexible. Many of the Joomla's plug-ins I've tried sport an abundance of confusingly labelled check boxes and drop down lists, so if you are new to administration, you will likely be more confused by Joomla's plugins (in general).
And the winner is...
WordPress is for you if you are new to blogging, or you just want an easy to operate blog intended for a smaller audience.
Joomla is for you if you want a full featured, flexible system, and you are willing to put time into being an administrator.