As quoted by Bob Arnson
"You can do everything (and more) that XmlFile supports with XmlConfig
but it requires extra authoring that's not necessary with XmlFile.
XmlFile is best at modifying XML files that you're installing (e.g., to
add an attribute reflecting the installed path of a file); it can't
remove the modifications at uninstall time but if your setup installed
the file, it will be uninstalled anyway. XmlConfig is best at modifying
shared XML files because it supports uninstalling the modifications."