Chiming in as an Ecobee user. The Ecobee is cool/nice/whatever, but what you don’t get from it vs the Nest is the “learning”. Yes, the nest follows exactly what you do initially, but eventually it starts to learn things like, “Oh, you regularly come home on Wednesdays at about 2 pm. Well, we’ll start adding that into the routine.”
The Ecobee is a straight schedule. I admit, it’s a highly customizable schedule, but it’s still just a schedule. It’s got tie-ins to ITTT, homekit, etc. You can add multiple room sensors and tie in automated vents that open/close based on the needs and occupancy status in a particular room which was the real big seller for me.
Nest has all of their smoke detectors that tie into it and have some really cool features.
You really just have to compare feature sets with your needs and understand that for the majority of add-on features, they will both likely support them in the future at some point.