I prefer wordpress because its so easy as SEO purpose and Joomla is not good bcz in this we cant easily changes in this for SEO purpose.
According to me,wordpress would be easy.you will find many wordpress SEO plugins compare to Joomla & Drupal
Wordpress is very functional. Just like with the WordPress Themes, if there is a specific functionality you want your blog to perform, there are programmers out there who have made WordPress Plugins that will do for you those things you would like to do. There are nearly 8,000 WordPress Plugins on the WordPress.org website ( wordpress.org/extend/plugins/ ), and thousands more that are not in the WordPress database. If you find a Plugin you want, just download, unzip, and upload it to the appropriate Plugin directory on your blog. After you have uploaded the Plugin, simply go to the Admin area of your Blog to activate the software.
Depends on your preferences, WordPress is quite hard though if you ask me (plug-ins are soo hard lol)
I think is not about the site machine you used, but how do you make the content of your site. Of course, how you build backlinks.