Load balancing lets sites scale by adding new servers as demand increases. Load balancing increases reliability. Load balancing increases reliability because Resin will automatically try another Java server if one fails. Beans serve as the model, JSP shows the view and Servlets control the application. The MVC methodology plays to the strengths of each technique and cleanly separates application function.
Applications become more comprehensible and maintainable.
In addition, the MVC separation separates projects by expertise. Database gurus can work on the model beans. Servlet hackers can worry about forms, sessions and state machines. Graphic designers and writers can focus on the HTML design. You can look at the JSP templates tutorial for an worked example.