JBoss is an Application Server while Tomcat is a Servlet container
So JBoss may be better than Tomcat in the sense it contains it, plus other components. That's it.
If you're not going to use those other components, you're wasting resources. If you need those other components then Tomcat is not enough.
It depends, probably your Architect has something else in mind.
I wonder what would he say if you ask him directly?
