Not much, on balance. Any expression of the form:

<foo a:bar="bat">Text</foo> can, in practice, be replaced with

<a:bin bar="bat"><foo>Text</foo></a:bin>

as far as I can tell. It is marginally more verbose, but syntactically it's perhaps a little cleaner.

The biggest issue I can see with that is with either xlink or xmlid, and neither of those are showstoppers:

<chapter xml:id="foo">Bar</chapter> becomes

<xml:target id="foo"><chapter>Bar</chapter></xml:target>

or some such, and as a consequence the identifier host becomes the target element rather than the chapter. Not a lot different from <a name="#" when you get right down to it.