JavaBeans are components which follow a particular method naming pattern, i.e.
classes which have getX() and setX()
methods and include a default constructor are considered JavaBeans. The idea
behind JavaBeans was to have a simple
means for providing drop-in usability of Java classes. For instance, you should
be able to drop a JAR with a bunch of
JavaBeans into a particular location in your IDE and those beans  become
available in your GUI designer.

Enterprise Java Beans are components which are meant to run inside of an
application server. EJBs are designed to allow
transaction, security and other requirements can be specified declaratively and
are provided by the application server.

Why should you use J2EE? Well, first it is a proven technology. There are
companies around the world using J2EE to
provide real solutions right now. Keep in mind that J2EE has a lot of peices
and you don't have to use all of them.
For example, if you use JSPs and servlets then you are using J2EE. Other Java
technologies may also work fine for you.
Since you don't specify what "other" technologies you are referring to nor do
you specify what kind of projects you are
working on it is hard for me to say anything other than that.