WS tends to be a more heavyweight system, with more back and forth, and more complex parsing demands (being generally XML based).  It is not obvious that that this adds value in the OpenADE domain, and REST interfaces are more likely to be implementable on a simple embedded device.  Though OpenADE is more concerned with server to server communication, it seems an unnecessary complication to use a different interface for in home device, and it seems likely that they will bleed into one another.  Also, implementing Web Service based projects is usually more costly for a given task.