It would seem that if nothing else, XQuery has much more momentum than XSLT while most implementations of XSLT is still on version 1.0 (atleast in the Java community).
The fact that XSLT was just recently added to OSB, and yet Oracle choose to go with a XSLT 1.0 implementation, is another sign of how XSLT seems to be left behind.
Many XSLT 1.0 templates suffer from over-complex expression there to overcome shortcomings in the old spec, which PROBABLY makes these transformations slower than they have to be, and therefore PROBABLY slower than the same solution implemented in XQuery .
http://goo.gl/3CBQUI