When using any CMS, be careful what add-ons and plug-ins you use. These could add vulnerabilities to your site.
Here is a nice reference demonstrating the differences of the 3 major content management systems.
During my time at my internship, we used a CMS called SharePoint. As stated previously, there are pro's and con's to any CMS.
Wordpress is a huge pain if you dont keep it updated! I spent 8 hours yestereday updating plugins and themes of pages that didnt keep their pages up!
There are many security plugins available for WordPress that should definitely be used! Here is a good list of some of the best security plugins. Keep your site safe!