Before choosing your system this is an other point you should think of.
Since the beginning, we're talking about Wifi (you should know this), Z-Wave and ZigBee. These are wireless communication protocols. Before choosing your system this is an other point you should think of. The first thing to know is that these two protocols are not using the same wireless range band. ZigBee often competes with wifi, working on the 2.4ghz band while Z-Wave operates on a lower band (900mhz). Zigbee is faster, open-source whereas Z-wave is closed and controlled by the Z-Wave alliance.