Java is used mostly in internet and intranet environments. This means that you have to code servlets and jsp's and most likely ejb's. Therefore SCWCD and SCBCD are important.
I'm working in a bank in the Netherlands. We hardly use web services. I believe that a lot organisations are sceptical about web services in internet environments. The reason for this is, is that the security of web services are still immature.
Therefore, if you are not yet a java developer for profession, I would recommend SCEA. Or you can study an application server, e.g. WebSphere.