Yep, Z-Wave's advantage is that they enforce the standards. They require that an end device from one manufacturer can work with any other manufacturer's controller.

That was a bigger deal when controllers were stand-alone electronics products, though. Being in the cloud, a controller like SmartThings can add one-off support for non-standard end devices at any time, so there's less need for everything to be on one standard.

thread is zigbee but more IPv6 friendly, they both run at 2.4Ghz like wifi and bluetooth do, which could be crowded and in short distance.

zwave by default is at 900Mhz so it goes much further than 2.4Ghz and it even has a long-range version(for a few km), that's another advantage of zwave.

all of them are low-power, all of them need a gateway or hub to talk to wifi and the internet, other than zwave is strictly co-operatable, zwave is also *much much* simpler, if zwave truly opens up, it could take over the competitors IMO.