Comparing XML string with different formats
Googling for xml compare c# produces countless results so I just review this code without suggesting anything alternative.




settings.IndentChars = "  ";



I find new string(' ', 3) is easier to understand then three (?) spaces.




    if (xmlA == null &amp;&amp; xmlB == null)
        return true;



This is questionable. I'd say it should be false.




var settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;



Don't you like object initializers?

var settings = new XmlWriterSettings
{
    OmitXmlDeclaration = true
};