My current understanding of the wireless technologies wrt to home automation:

- wifi is most reliable, secure, easiest to debug, but usable only for mains-powered devices due to higher energy consumption

- bluetooth LE has lowest energy consumption, best for unreliable broadcasting of data (e.g. temperature sensors), but has shorter range

- zigbee is best for battery-powered devices where reliable communication is needed and is initiated by the device (e.g. switch, window/door sensor)

- zwave is best for battery-powered devices which need to quickly receive data (e.g. door lock or directly controller radiator valves), but security seems problematic according to some reports