Are the TV's co-located or are they in separate rooms?

I prefer wired and I'll spend the extra effort if wiring is at all possible. I'm not the greatest fan of Zigbee and I avoid it when practical. Global Caché -- sure, I use it quite often, but not in an RTI context. Wired RTI processors at each remote location is solid -- resulting in a much more responsive, reliable system. If this is a demo system, I think that it should be representative of what you would actually recommend and sell to a customer.

If you use XP-3, rather than Global Caché, you'll spend a lot less effort setting up the system and changing TV models later will be much easier with an all RTI system. That said, if you already have developed your IR codes for Global Caché, you have already worked through most of the setup grief.

My big beef with Zigbee is that it does not roam very well, however, in your case the processors will not roam.