I personally like joomla because the back end of it is a lot more confusing and harder to first install.
Best for what? No one CMS is the end-all/be-all. It's best to have a few platforms in your arsenal that have specific strengths. Joomla 1.5 now has an more extendable core, and a plethora of plugins, but it's too complex for some projects. WordPress is powerful and has strong blogging features at the core, and is becoming a CMS in its own right, but the way it handles the multi-user environment still is very "bloggish" and does not quite yet at its core have the shared user multi-functionality of a more traditional CMS (ala Joomla). Both Joomla and WordPress may be too much for someone who wants a more boutique site that is focused mostly on the site owner's activities which may or may not include blogging. In that case, you have CMS platforms like Website Baker, CMS Made Simple, etc. There isn't a magic solution. There's just the solution that best meets your needs, which can change over time and from project to project.
At competition Packt Publishing, Joomla CMS it has been recognised the best by free CMS. In total 70 control systems of a site participated in competition, in the ending there were only five: Drupal, e107, Joomla!, Plone and XOOPS. From five finalists Joomla was the youngest project and, despite it, has won! The prize for the first place has made 50000$. The second and third place at competition have got Drupal and Plone accordingly.
I use Joomla for building big or small website. Wordpress is for blog mostly autoblogs. I don't agree that Joomla can't be used for big websites because many people use it for big websites as well. Joomla is working for me now.
I use Joomla a lot and Wordpress also. Putting them in two categories is correct but lately using the latest Wordpress with some of the advanced professional themes and plugins (Widgets) I feel that Wordpress is becoming more like a full blown CMS as time goes on. I know Drupal is popular too but I have not used it yet.
Are you joking In Packt Publishing 2008 Award Drupal is the Overall Winner and Best PHP Open Source Content Management System
I love joomla. The functionality and capabilities are great for anyone who wants to develop any type of site.