They have a different model -- one is better for documents, and one is better for programs/data XML and HTML are attributed text, while S-expressions are more

They have a different model -- one is better for documents, and one is better for programs/data XML and HTML are attributed text, while S-expressions are more like a homogeneous tree If you have more text than metadata, then they are more natural than S-expressions e.g. The closing </p> may seem redundant, until you have big paragraphs of free form text, which you generally don't in programs