As @duffymo points out, JBoss uses Tomcat for its web container so better makes not much sense if we compare equivalent things (i.e. Tomcat and the web container part of JBoss). And if you are not going to use JTA, EJBs, JMS, JMX, etc, there is no real advantage at using JBoss, especially during development (Tomcat is lighter and starts faster, this is often appreciated by development teams).
There are some cases where you could prefer JBoss for production though (I'm still assuming you're not using EJBs, etc):
- The production team is trained or used to use JBoss in production, tools (deployment, monitoring, etc) are tailored for JBoss.
- The company has a support contract for JBoss (although you can also get support for Tomcat).
But I'm not sure this is what the app architect meant. I would try to discuss this choice with the architect, maybe he has a rationale explanation. And if really JBoss has to be used in production, you can always use Tomcat or Jetty during development.