Internet Of Things / IoT / Connected Home / Smart Houses

Nest has no radiator integration... it's really just on/off control for the boiler. Smart yes... adapts schedule, learns how long it takes to get the room with the thermostat to a specified temperature, can learn how you manually override the schedule and make those adjustments for you... it makes set it and forget it complete... but it also is just an on/off switch. The best on/off switch for sure, at least this works when the internet is down (I switched from Hive to Nest precisely because an internet outage rendered my heating useless).

The smart integrations from boiler manufacturers are also on/off switches. Typically tuned to the boiler to make them more efficient in their ramp up of heating. Not as intelligent as the Nest, but if you're using a static schedule then they do this via a nice app and allow you to trigger heating out of home and will ensure the heating is fractionally more efficient.

The real difference comes when you jump to Tado. Still an on/off switch for the boiler, but now with individual radiator control. This is done by having the TRVs on the radiator be motorised, and it will combine enabling the boiler with adjusting radiators to give per-room control. Some reports in this thread of Tado TRVs being noisy when they adjust (i.e. when you're sleeping and they adjust to enable heating before you've woken)... but you get per-room control.

What I believe the decision chart looks roughly like is this:

• Small apartment and deep pockets? Buy Nest
  
• Small apartment and shallow pockets? Any smart thermostat will do, the boiler recommended one is good, the cheaper Nest is good
  
• Large home and radiators but only desire whole home on/off control? Buy Nest or boiler recommended smart thermostat
  
• Large home and air-con? Buy Nest - this is the only time you'll fully utilise a Nest, it was made for the US market and now it will keep each room (air-con unit zone) within a lower and upper temp/humidity range
  
• Large home and radiators? Buy Tado - this is the only time you'll fully get per-room control with radiators. No point doing this on a single level 1/2 bed flat as the internal temps will even out and the benefit is hardly there