Tomcat is a Web Application Server. WebSphere and WebLogic are full
J2EE environments, which must include a web application server. As previously posted, neither is an IDE (Integrated Development Environment), although some IDE's include a WAS (like TomCat) or a J2EE server (like
JBoss).
For example, a J2EE environment must include a EJB server, which is not handled by TomCat.
That said, as a designer it is always good to question if you need a J2EE framework, or if a web application server will do. I have often sold management against the need of a a J2EE framework, and instead settled for just a WAS. More often than not, a WAS is sufficient, especially when using frameworks like Spring, which make EJB's unnecessary.
Some questions to ask - what kind of persistence model do you want to support? Is clustering needed? Whats is the failover model for the app?
As a developer, I often develop and
test in a WAS, then deploy to WebSphere or JBoss.