Anecdote from the other side: my zwave devices just work for 8 years now, while there are times some zigbee devices just don’t respond. I suspect the zwave network is more stable because all routers are powered all the time, while I have lots of zigbee bulbs that are behind a real switch so they leave the network if I turn the lights off. There seems like to be no way in zigbee from preventing those devices to be used as routers.