What is the best technique to use for comparison

What are the best technique available for comparing two xml files contence?
Meaning generating equal or not equal as a result on the contence of the 
both xml files. It would also be good to learn how to relate differences to 
a nice output format.

Regards
Johan 

 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list