I don't know that either of them is "better" - that's a rather qualitative judgement based on not knowing why you're debating the two exams. Both of them, certainly, would show that you know how to use an application server, and have some experience with coding
J2EE applications.
I would second the suggestion to do the Sun exams first (I'd add IBM's 483 - Enterprise Connectivity with J2EE - to the list too as an exam that demonstrates familiarity with J2EE development), since they're more generally geared towards J2EE development than a specific server product.
The "better"ness (to use a really badly made up
word) of the two exams would really be more determined based on what your employer/clients use, or what the employers that you're looking at use. I don't think you can necessarily go wrong with either one, but the value would be enhanced if you're going to end up using one server over another.
Just my two cents.
