The million dollar question-

Not all HVAC techs are the same- the opinions are based upon what they experience rather than facts.
If you talk to a high level contrssl tech (like me), our opinions are what is in the inside and how well it can control - last be not leest, the number of issues it has had over the years.

Ecobee - Came out in 2009, deveoled by Toronto Canada firm. Stuart Lombard developed the company in 2007. In 2008 he raised $8- million in funding for this product line
So - Ecobee has 16 years in the making of the device

Google Nest - The nest was originally owned by Nest Labs ( co-founded by apple engineers Tony Fadell and Matt Rogers in 2010. The thermostat was introduced in 2011. In 2014 Google acquired Nest Labs. So it has 14 years in the perfection of their programable line up.

Here is what you are missing - now each of these do the same, in most cases a learning thermostat will not fit your needs. Rarely is the human schedule the exact same every day. So some companies have ways of doing things better based upon experiance.

Honeywell - Founed in 1906, or 119 years ago, that is 7 times longer than either of them. I'm sure we all know about the history of them, know the name- but how about the product lines?
T9 or T10 are the two top of the line programmable thermostats they offer, along with dozens of lower end models. So why the T9 or T10? I personally love the T10 as it also has a varible option the others do not have. The biggest differance bwtween the two is tat one extra option that you can contol a humidifier or dehumidifier. It has the option much like the others to have a remote sensor and all of them can read humidity, not just temperature. Prior to these two that have only been out since 2019, there are many others that do simulare, but the engineers decided to go beyond all others with this line. The T6 pro was very common and has been out since 2016 which was a nice upgrade from the T5. But in truth, we need to go way back to thhe 7000 series. It changed the market, thus is what drove the oher companies to try to match or beat them. I have never seen an electronic honeywell thermostat fail. They take extream care in the development of their products, elimiting issues and testing on many brands of furnaces / AHUs. They also have the solution to the 4 wire probelm. The other two have seen many issues with a 4 wire system. The T9 comes with this adapter so you have full functions with out issues. It is an option of the T10, but with humidity control the T10 is nice.
So why do I like Honeywell? Besides the track record, the T9 and T10 are easy to run, simple to program, offer Geo-fencing with multiple smart devices. If you have multiple sensors, you can control your system and program it to read which sensors at which times. I have it ontol temp at night by only the sensors in the bedrooms. In the day time, only the living space. Recently I needed to control more than one facility. Honewell does this flawlessly. I. can choose wwhich facility and then it gives the list of all thermostats in that facility. Soimple yet powerful.

Seen so many issues with the other two, you must have a 5 wire cable, power robbing can cause issues in some brands.

Do not over look Honeywell - These two are by far the best option on the market today. Newest tech and easiest to set up.

Like I always say - our opinions are derived from our experiences - being a high end controls tech along with a few others means I have tested and delt with many types of control systems.

Eggs

 

I went with the Ecobee Smart Thermostat Premium because I liked the built-in Alexa and the remote sensors, which help balance temperatures in rooms that always ran hot or cold. A friend of mine swears by the Nest for its learning features and how seamlessly it ties into Google Home. It really comes down to which ecosystem you’re already using. Both save money long-term and make life more convenient. Picking one felt like looking up the Southwest Gas phone number, straightforward, but still worth double-checking details!

 

I went with the Ecobee Smart Thermostat Premium because I liked the built-in Alexa and the remote sensors, which help balance temperatures in rooms that always ran hot or cold.

Thanks for your helpful reply.

 

FYI - all three of them do this
I just perfer the way Honeywell does it, more control, but in the end - All three do the same -
Personally, I do not want my Google Home to cotrol the thermostat - All I need is some kid to say "Hey Google, turn the heat to 78°, although it can not got past 76° because of the limits I put in it.

Eggs