Good question. I think it boiled down to reading lots of "will x-brand work with x-brand?" questions, and it seemed like a bit of a mess. If I bought a certain Zigbee hub, not all zigbee stuff was going to work.

It's my understanding that Z-wave "fixes" that by having a standard, and if a company wants to sell Z-wave stuff it has to be certified and licensed. This increases the cost which is passed on to the consumer, but the end result is that anything called Z-wave works with any Z-wave hub.

It's still not perfect, but my experience has been pretty good overall. I have quite a few Z-wave devices and most of them are extremely stable. I have one or two devices that are problem children, and I have to "ping" them to wake them up sometimes. Compare that to WiFi, which my house is also heavy on -- and I currently have two devices that simply won't connect to WiFi after updating the firmware. I'm going to have to take them apart and physically flash them again.

Every protocol has it's own problems, but overall I've been happy with Z-wave and WiFi.