I will say, honestly, of the options you can realistically use in the US, you can use:
* Z-Wave .. lots of vendors.. fairly standardized command classes, can do Lighting, Climate, and Security
* Insteon .. One main vendor.. Inexpensive...can do Lighting and some sensors
* KNX .. KNX is _the_ gold standard for automation (itself descended from the European Installation Bus EIB), few vendors in the US, (Element Controls being one), but a high degree of redundancy and reliability. Can handle lighting, climate, and security.
* 1-wire can provide various sensors that can be read and reacted to via events.
* a GC-100 can provide a connection point for contact closure sensors and infra-red, as well as 1 or 2 RS-232 ports, and relays.
And of course, drivers can be written very quickly to support more and more devices, either directly, or through an interface.