The question
you should be asking is which is more applicable to you given your experience and the company you are working for or are looking to be working for.
If you know
J2EE 1.3 well and feel comfortable with that skillset, then I would recommend taking the currently existing SCBCD exam. There are a lot of companies that have not yet made the jump to
Java EE 5 and won't be in the foreseeable future (such as mine) Existing applications will still need to be maintained, and there will be plenty of work for the near future with applications conforming to that standard.
On the other hand, if you're just now getting into EJBs or Java EE, then I might recommend waiting until March/April when the SCBCD 5 exam goes general-release. (There's no point rushing your preparations purely for the sake of taking the beta.) There is a lot that has changed, so there are going to be companies that are not using this standard yet, but there will be a growing market for the skills covered by this exam.
I hope that helps you make your decision. Good luck, either way!