@dered - i am sure WP is the best solution for you but not necessarily the next person, please expand your reasoning...
@sunseven - sorry to say you are very mistaken if you think Wordpress is THE most flexible platform of the three.
@Hijinx - all three platforms have had and will continue to have vulnerabilities
Script kiddies will take advantage of security holes of poorly written third party plugins not generally the main core code.... hence dont use badly written plugins and always keep your scripts up to date...
There are plenty of posts on this forum about what people consider to be the best blog, cms, solution for them and i am not sure if this warrants another thread about the same subject...
At OP if you want information about Joomla from someone who uses it daily for iterrnet marketing, who teaches it, who develops addons for it, designs templates for it, and has spoken alongside the founder about Joomla and SEO, and who has built a financially successful business model around it then drop me a PM.