Certificate compliments to experience.
Demand is for EXPERIENCE. So I won't compare 'SCDJWS vs SCBCD', but would compare '
JWS Vs EJB 3'
JWS Experience - Instant demand
EJB 3 - Big change compare to EJB 2.x - development time is less in EJB 3 but concept wise Session/MDB are same. JPA is new big thing in EJB, so demand will improve in near future.
other points if you are new to JWS & EJB
there are books for EJB 3 which are helpful to prepare for cert
there is no single book to cover objectives of JWS cert, so you would need to study it from multiple source
Last but not least : Both are different & mandatory for a J2EE Developer, and you would need both, it's your choice which one you want in your kit first.