First of all Tomcat is a WebServer and has a JSP/Servlet engine called Catalina to process JSP and servlet requests. It cannot process EJBs whereas, JBoss is an AppServer.
Second, you are trying to compare apples with oranges which does not make any sense.
So please first ask yourself what ur requirements are; i.e. do you want to deploy EJBs or do you jst want to run JSPs and servlets. There are many more things that should be considered like resource allocation in terms of memory usage, ease of use, start up time etc.