I don’t intend to draw any wires, battery powered was a main request for me. Since i don’t have an option to hide them it would be ugly, so it’s a deal breaker for me - i already have too much of them around. Also, i’d have to buy/make a controller for them…
I wanted wifi ones, but they are pretty scarse, so i ended up with zb connection, and so far so good (fingers crossed).
But, that’s why there are both variants on the market. I like this, you like that, problem solved.
But, as you said, there’s absolutely need to do a research BEFORE buying anything. I did my part, so i ended up with sonoffs and connecting them was a matter of 1 minute. I do that for each new thing i buy: first i double-check if it’s HA compatible 
i did that before buying climate, air cleaner….
Wifi and battery powered isn’t a great match. WiFi typically uses a lot more battery. Zigbee needs a lot less power but if the TRVs are the only devices in your network you probably will have limited range, as they are endpoints, not routers. Usually you need a few mains powered ZigBee devices that can serve as routers in the mesh to get a well functioning ZigBee network. Lights or a smart plugs usually fulfill that role. If you live in a small house and your controller is located centrally you might get away with it.
In my house, the ZigBee network is at least as reliable as the WiFi.
Yeah, i guess that’s why it’s hard (if not impossible) to find wifi trv’s…
I do have battery powered wifi device, but it’s only window sensor (converted to “door unlocked” device), so it wakes up only when lock / unlock my door, and it’s powered by two AAA batteries, so it’s been a year now and still working.
Trv however constantly communicates with HA, so i can imagine (too) frequent battery changes.
