Following are benfits to use Joomla:
* It is OpenSource means download & modified at free of cost.
* It is CMS, You can add different types of content in same or different category can be added and published on your website.
* Thousands of Free components are available in extensions.joomla.org/
* User Modules, User Role and permission are in built with joomla.
* It follow MVC
* You can also update your old joomla from admin section.
* Easy to development websits in joomla.
* Various template are available at free of cost and can apply within one click.