HF EJB alone can help me through the IBM 484 EJB objectives? Certainly not! Looking at the objectives, there are many things in there aside from EJBs like JSP, JDBC, JMS, JCA, JTA, just to name a few. Besides, the whole exam is tainted with Websphere flavour while the SCBCD test is vendor-agnostic.
HF EJB really focuses on EJBs solely and no particular vendor.