My 2 cents … I’ve got two ecobee’s and I love the remote sensor concept. The ‘support’ from Ecobee is fantastic; I had a new AC system installed last week, and the new system had 2-stage heating and 2-stage cooling. The installation tech needed to know about some of these details (thresholds, durations, etc) and so I called ecobee support. Got a live, ‘good English-speaking’ person right away, and she was able to answer all questions. Today I had an issue with readings, and I used their ‘chat’ feature; got a great guy who helped me. I’ve had this experience several times. Also, their ‘chat’ feature is available on their main website, and they don’t put you through any barriers to reach them.
In contrast, I was considering a Nest a few weeks ago but had a question; I could not find any way to reach a person by chat or voice, easily.
The big downside to Ecobee IMO is the looks. It’s a big device, shiny black finish - VERY visible on the wall (The nest can be bought in a subtle off-white color, which is why I was considering it). The workaround - locate the main ecobee thermostat INSIDE the ac closet, and rely entirely on the remote sensors for temperature sensing, and use the phone/web apps for management. You can totally ignore the temp of the main thermostat and just read from the remotes. I’m even considering painting over the main ecobee face to hide it 
… but you must use the main screen for a few advanced settings.
Edit to add: I found this thread while about to post a question about ecobee data; I’ll create that thread and post a link here. The issue is - while ecobee reads data every few minutes, and the data is changing, that changed data is not making it over to SmartThings. Last night, my AC kicked in twice between 11pm and 2am, but neither event was seen by ST. The events at 11 an 2 were … so it’s getting ‘some but not all’ data. I’ll post separately …
ETA - here’s my post about ecobee data integration …