> The XML tag style is much, much easier to work with when you're dealing with markup.

Having explicit end tags makes it harder to make well-formed documents that don't clash their closing tags.

Consider a very typical sort of HTML error:

    <table>
      <tr>
        <td>
        </tr>
      </td>
    </table>

Interleaving tags is never correct, yet XML allows us to do it (and I've seen it happen a lot).

The comparable S-Expr shows how it is just plain impossible to interleave tags:

    (table
      (tr
        (td)))

You might ask yourself, "which close paren closes which list?" if the document were particularly gnarly. But if we're talking about particularly gnarly documents, then XML can be just as ambiguous. You'd be using a text editor that highlighted matching parens for you, at that point, just as much as you'd be using one that highlights matching close- and end-tags.