The bikes you are considering are all great bikes. They are in the same price range and are similarly equipped. You won't go wrong with any of them. I liked the Trek 5.2 and the Synapse 3 and chose based on color. The Domane came out after I purchased my bike so I was not able to test ride the bike. If you want to compare road feel on test rides make sure the tires are inflated to same psi; that can make a huge difference in road feel. If you want a smoother ride, 25 or even 28mm tires will run at lower pressure and eat up some of the road vibration. The Domane might be the right bike for your road conditions.