I use Comfort mostly, with Eco for longer motorway journeys and when using adaptive cruise in stop/stop traffic. If I want to go faster I just put the gearbox into sport mode rather than select a different drive mode, as I don’t particularly feel the need to add weight to the steering. (I’m driving an A3 without adaptive dampers.)
The main differences beteeen comfort and eco, that I can see, are auto-cruise behaviour (gentler acceleration in Eco), aircon mode (Eco in Eco) and (I guess) throttle mapping (less responsive in Eco?).