If you are talking
about this IBM exam then i feel Sun's exam is better as from what i could make out from the contents of the IBM version its more focussed on development alone and not the design and architecture aspects (Sun's exam has 2 sections devoted to those). Also Sun's exam covers more ground by covering topics like JAXB, JAXR and JAXP (SAX, DOM and TrAX). Its more well organised and covers all essentials for webservice programming and that it covers standard APIs alone (for eg, no UDDI4J here), is the most important point in its favor.
SCJP 5.0 (90%), SCDJWS 1.4 (88%), SCWCD 1.4 (82%), SCBCD 1.3 (85%)