Please, check my question and answer in the below question. XML Parsing performance DOM vs XOM
I tried both using the same algorithm.
They had the same CPU time. XOM Parser was 70% faster when it comes to Up time of the whole process. XOM parser had 25% smaller memory foot print as well. However, XOM needs more lines when it comes to coding as you need to loop through elements and cast nodes to elements yourself.
Regards