I replaced my ecobee 4 over a year ago with the Zen Thermostat and have no complaints, my entire HVAC is entirely automated by house average temp of all inside devices with temp sensors and house average humidity in conjunction with the Ambient Weather Station outside temp to determine heat or air conditioning all via Node Red.
Basically you should just pick the zigbee one that you prefer the appearance of, as by automating the same way I'm doing your literally bypassing the "purpose" of the thermostat's functionality. With the automation you're simply just making an automated wall switch that turns the HVAC components on/off. The actual temp of the thermostat is essentially meaningless. So it boils down to which one you like the looks of better.
Quite true - I'm keen to avoid units that dont have direct device support from HE (eg the Pearl) as I want to be able to control the fan on my Heat-Pump unit independently from the hating/cooling functions.
TBH I like the KONOz looks the best but cant find any in stock in white.
I haven't tried any of the others (I'm currently using a Z-Wave thermostat my utility company provided as part of a free energy-metering hub/package they sent me...they never said I had to pair it to their hub ), but I used to have a Zen Thermostat. Still do, if anyone wants to buy one used.
My only problem with it is that it seemed to do odd rounding with setpoints. For example, I'd set the setpoint to 55 degrees, and it would come back reporting that it was something like 54.9 or 55.1 degrees. This isn't problematic for most things aside from automations where you expect a range of values and have to plan a bit more carefully to accommodate possibilities slightly outside them. After a recent thermostat firmware update, it also seemed a bit wonky reporting or setting (I can't remember which or both) the fan operating state.
I'm curious how well the others work. I certainly like the look of the KONOz (not so much the price), but the Pearl was made by a well-loved Zigbee device manufacturer, so I'm sure it's not terrible. But as suggested above, mine is mostly automated, so as long as it works well with that, I don't really care.
For me that always means it had better be VERY simple to change the current cool/heat set point at the thermostat itself. She won't use voice, wants to manage stuff directly at the unit on the wall "Just like I always have." [sigh]
I'm guessing that this was the result of some C-to-F conversion, but I have no idea and never tried it on Celsius. For all I know, it could be doing the same thing there and just be some weird floating-point-rouding error it would do with any scale (reporting tenths of a degree Fahrenheit isn't odd but isn't super-common on thermostats; my understanding is that this is more common with Celsius). if you use it, hopefully your luck is better or it doesn't end up affecting any automations regardless.
Interesting video on the US and our on-again off-again relationship w/the metric system. I'm all for metric...so completely tired of doing cups, pints, quarts, and gallons, or trying to see if the measuring tape point is 5/8 or 3/4! [eek!!]
), but I used to have a Zen Thermostat. Still do, if anyone wants to buy one used. 
