Enterpirse Connectivity will cover
EJB and RMI, CORBA, C/S architecture to some extent.
While IBM WebSphere AppServer Advanced Edition is more focusing on WebSphere product knowledge in J2EE.
I passed Enterprise Connectivity before I went for WebSphere. Coz, I think WebSphere is much easier to me.
All product knowledge can be learned through experience, from redbooks. While OOAD and Enterprise Connectivity requires solid background, if you want to pass with high scores.