It does depend on the home, with my old open plan house, heat rises, so one thermostat down stairs between the two rooms was good enough. This house has doors, so a single thermostat will not work, I have 16 thermostats, two on the wall, and 14 built into the radiators thermostatic radiator valves (TRV) I don't have an option of using ebus, but all TRV's gradually open and close, and the wall thermostat only turns on/off a few times a day, so in real terms the TRV's do all the work.
So if we look at options, Hive does not have ebus, Nest does not connect to TRV's, Tado one has to be careful, some will connect to TRV's and have ebus, but not all, Honeywell evohome was one of the first, and does connect to TRV heads and has the option of an OpenTherm add on, and the Drayton Wiser also has an add on, which can also work OpenTherm and connect to TRV heads. So that gives three makes.
The comparison is really how good the TRV is, the thermostat is really only a hub, the Wiser TRV claims to work out re-heating times, so set to heat to 20ºC at 8 am and it works out when to turn on to get room at 20ºC at 8 am. As to if it works not a clue.
I have three makes of TRV, Energenie, Kasa, and eQ-3, non connect to my wall thermostat, however the algorithms in each one vary, the Energenie the anti hysteresis software is OTT, set to 20ºC at 7 am and it is nearly 11 am before it gets there, so I set to 22ºC at 7 am and 20ºC at 8 am and then it is at 20ºC at 8 am. However this means any idea of geofencing is not going to work. I did try geofencing with the Energenie which uses IFTTT, but it was not much good, I have also tried it with the wall thermostat, which is Nest Gen 3, this was also a failure, you can't set the distance with Nest only control is Eco and Comfort setting, and there is simply not enough time for it to re-heat from 17ºC to 20ºC in the time it allows.
I have also had it completely fail when the EE mast went down, the real problem was every time I approached the thermostat the built in PIR would detect me and turn up heating, but since not detecting phone, it would then turn back down to Eco setting, so it took some time to work out what was going on, the geofencing was then disabled.
I can with my phone look at 4 out of 9 electronic TRV heads and the Nest Gen 3 thermostat and adjust setting, any where that I have phone signal, the other 5 are bluetooth, so I need to be really in the room to adjust with phone. However it is rare I need to use phone, just spent a few days in the North East went to Bemish, and yes set Nest to away, and one return called into services where I turned heating up again. But this is only time this year, I simply use pre-set times.
I will look at temperature in the summer, shown by the TRV, and decide if the AC needs turning on, but that's because it is a cheap AC and the condensate bottle will over flow if it runs too long unattended. Better idea would be a hole in the wall for the condensate pipe.
I thought being able to control heating from the phone was a really good idea, however now I have the option, I find simple times work a lot better.
The Kasa (TP-Link) is by far the best of the TRV's I have, and it does allow me to look at how it has done over the day,
remember my boiler is not a modulating one, runs on oil, so will never work as well as a gas modulating type, but it does seem the comparison has to be how well the TRV works with most homes, the wall thermostat/hub only relays info to the boiler.
Also although you may need some linked TRV heads, likely you don't need all to be linked, when I got my eQ-3 in 2019 they cost me £15 each, gone up since brexit, but a Wiser TRV costs £37, not much, but when one has 14 radiators it mounts up, EvoHome £70, the non linked Kasa £35, Tado £48, OK still need to wall thermostat as well, but it does seem Drayton Wiser is likely the cheapest option.