Tried to use @Jukka Matilainen's answer but having issues with white-space (one of the files was a huge one-liner). Using --format helps to skip white-space differences.

xmllint --format one.xml > 1.xml  
xmllint --format two.xml > 2.xml  
diff 1.xml 2.xml  

Tried to use @Jukka Matilainen's answer but had problems with white-space (one of the files was a huge one-liner). Using --format helps to skip white-space differences.

xmllint --format one.xml > 1.xml  
xmllint --format two.xml > 2.xml  
diff 1.xml 2.xml  

Note: Use vimdiff command for side-by-side comparison of the xmls.

To expand further on Jukka Matilainen's answer:
Using --format helps to skip white-space differences.

xmllint --c14n --format one.xml > 1.xml  
xmllint --c14n --format two.xml > 2.xml  
diff 1.xml 2.xml  

Note: Not enough reputation yet to comment on the original answer so adding my own answer.

Tried to use @Jukka Matilainen's answer but having issues with white-space (one of the files was a huge one-liner). Using --format helps to skip white-space differences.

xmllint --format one.xml > 1.xml  
xmllint --format two.xml > 2.xml  
diff 1.xml 2.xml