This was $10 less on prime day, but it’s still a good deal and historically these have not gone on sale often.
This is the newest model, one generation newer than the ecobee 4.
Superficially, it’s very similar to the 4, but there are a few improvements.
This is the first model which can work with a WiFi 5.0 GHz band, not just 2.4 GHz (that’s what “dual band Wi-Fi“ means in the product description.)
It offers some of the Alexa features which were not included with the 4, including Alexa calling and Spotify.
It comes with the newer generation smart sensor.
Other than that, it’s basically the same as the 4.
Works out of the box with smartthings, HomeKit, and IFTTT.
I have heard rumors that with the new V3 app you can’t change thermostat modes through the official features anymore, but I don’t know if that’s true.