SCWCD is about Servlets 2.4 and JSP 2.0. You'll learn how to make web applications using servlets, JSP and JSTL.
SCBCD is about EJB 3.0 and JPA 1.0. You'll learn how to use enterprise Java beans, and how to persist data using JPA.
What are you interested in ? SCWCD sounds like a good start. You'll find all the details at Oracle's homepage.