I always like to emphasize that SCJA takes a very broad view of Java, where as the SCJA exam is very syntax focussed.
The SCJA credential lets people know you have an understanding of everything from micro devices, to
Servlets and JSPs, messaging, OOA&D and of course, syntax.
On the other hand, SCJP is really syntax focussed. To pass the SCJP exam, you need to know some fairly esoteric idiosyncrasies of the JDK. At the same time, a successful SCJP holder need not know a thing about a Servlet or a
JSP.
I like the well roundedness of the SCJA exam. Of course, I may be a bit biased.
-Cameron McKenzie