The two main advantages were XML parsing performance, and the ability to embed XML directly in the XHTML. For phones of the era, the performance benefits are ob

The two main advantages were XML parsing performance, and the ability to embed XML directly in the XHTML. For phones of the era, the performance benefits are obvious. As for XML embedding, it'd give you the ability to embed SVG, MathML, and any other XML language directly. This avoids a second retrieval/parsing step, and allows extensibility without changing the XHTML spec.