I wanted to start a discussion what is the better choice for an application server when building an enterprise J2E application? Should one go for a Tomcat + Spring combination which provide light-weight simplified alternative to JEE container or should more heavy weight app server like JBoss be considered?

I have found some resources on Stackoverflow that provided me enough information to think about:

1. What are benefits of JBoss AS-based application architecture?
2. When to ditch a J2EE container (i.e. JBoss) for straight Tomcat
3. Should I go with Tomcat or a full J2EE container?