I had a 2017 Domane SL6. I have since replaced it with a 2019 Giant Defy which I prefer.
The iso speed did give the Trek a bike more compliance but the Defy is still plenty comfortable enough and the ride feels a bit more lively and connected.
Not really a fan of the added complexity and weight of the iso speed either with the weird headset arrangement, little bearings, pivots, pins rockers etc.