my predection is that Zeroconf will win.
simple because it's simple. it doesn't try to define the world or force new definitions in some 'standard' format.
i've been going over the code needed to add Zeroconf support to an app on OSX, and it's just a few lines. if you can handle unix sockets, which are pretty easy by themselves, you can easily add support for this fantastic technology.
that UPnP uses SOAP is enough to make me shutter. that's quite a bit of work and knowledge needed to write even a simple app like the picture sharing example that Apple provides.
making things simple is always a good idea..