1. Bootstrap: Joomla 3.0 is Bootstrap. With basic CSS already integrated into Joomla 3.0,while Joomla 2.5 is without bootstrap.

2. Less: LESS is a dynamic stylesheet language which has been integrated into Joomla 3.0. Template development has been changed by using LESS.While Joomla 2.5 is without LESS.

3. Faster steps installation: In Joomla 3.0 installation process steps are much simplified than Joomla 2.5.The installation process is now only 3 steps compared to the 7 steps procedure in Joomla 2.5.

4. Article Manager interface : In Joomla 3.0 article manager interface has been changed completely, now it provides much better layout compares to Joomla 2.5 Article Manager. Joomla 3.0 includes a better organized filtering system with more options available, and better defined icons.

5. Guest user group : in Joomla 3.0. It is available as default upon installation which is not available as default in Joomla 2.5.

6. Front-end template : Joomla 3.0 provides responsive front end template for eg.protostar with a power of bootstrap facility. While Joomla 2.5 is non responsive front end template.

7. Template Beez3: Joomla 3.0 provides an updated Beez3 template option which is not available in Joomla 2.5.

8. Mootools vs jquery: Joomla 3.0 is packaged with JQuery in the core Also Mootools option is still available in the back-end while in Joomla 2.5 is not packaged with jquery in the core.

9. Joomla 3.0 is now responsive. The front-end interface will have the responsive built-in feature while Joomla 2.5 is non responsive.