I am very surprised nobody mentioned Microsoft's XML NotePad
It's free and it can create a pretty good comparison, telling which elements/attributes have changed, moved, been deleted, etc.:
(Sorry if the screenshots are a little wide).
![image](https://www.your-translations.com/images/XML%20Notepad.jpg)
![image](https://www.your-translations.com/images/XML%20Notepad_compare.jpg)
You can also apply XLSes to the XML file and do various editing operations. Well worth a try.
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