Depends on what you want to be doing in the long run, as to which one to tackle, I would say - Sun's designed the two exams for different roles.
SCBCD is a programmer's certification for EJBs and the like, while SCEA is aimed more towards those interested in software architecture. There's places for both in the grand scheme (I'll probably eventually circle back and get SCBCD myself), but it depends on what you want to be doing. If you want to be developing business components, I'd say brush up on EJBs and go for the SCBCD exam. Otherwise, brush up on design patterns and go for the architect's exam. Either way, it sounds like you have some studying ahead.
Theodore Jonathan Casser
SCJP/SCSNI/SCBCD/SCWCD/SCDJWS/SCMAD/SCEA/MCTS/MCPD... and so many more letters than you can shake a stick at!
Using Head First EJB you should easily obtain a SCBCD 1.3 which should ease your subsequent SCEA preparation pain considerably (as evidenced by some of the EJB related inquiries in this forum). The SCBCD 1.3 requires detailed knowledge of a single specification EJB 2.0. There is the possibility of an SCBCD update (to EJB 3.0) by the end of the year. If they stick to the single specification concept that should be "no big deal", though its going to take a while for the study-guides to catch up. However Sun may be getting a bit tired of EJB being criticized and decide to add an "Designing Business Components" objective (similar to the "Designing Web Services" on the SCDJWS) where you have to determine in a scenario whether EJB is an appropriate solution and if it is, exactly what aspect is optimal. If that is the case then the next SCBCD may be somewhat harder than the current one.
However you still have the option of simply using Head First EJB as part of your SCEA preparation (through Part 1 only covers EJB 1.1; however EJB 2.0/2.1 would be handy for Part 2).
I personally think you should go for SCBCD, as it covers EJB portion of the enterprise architect certification as well. Secondly, It will help you in Part-II for SCEA as well. So if u are learning all of SCBCD course, why not get the cert as well