Here is a nice comparision on DOM, SAX, StAX & TrAX
(Source: http://download.oracle.com/docs/cd/E17802_01/webservices/webservices/docs/1.6/tutorial/doc/SJSXP2.html )
Feature StAX SAX DOM TrAX
API Type Pull,streaming Push,streaming In memory tree XSLT Rule
Ease of Use High Medium High Medium
XPath Capability No No Yes Yes
CPU & Memory Good Good Varies Varies
Forward Only Yes Yes No No
Read XML Yes Yes Yes Yes
Write XML Yes No Yes Yes
CRUD No No Yes No