The 3T is probably the one with the most aero testing and development. It is supposed to be faster dirty than when clean (turbulent air can follow sharp bends better than smooth laminar flow). Gerrard Vroomen had a hand in developing it (founder of Cervelo). Vroomen also started OPEN and designed the Open UP & Upper. The UP is crazy fast with a super short chainstay and feels lightning fast, but also has a moderately aggressive front geometry to keep it excellent handling on gravel. The thing is magic! Our shop sells gravel bikes by 3T, Open. Salsa, Bombtrack, Giant, Jamis, Wilier and Felt. I am on my third OPEN now as it is a magical balance of speed, COMFORT and handling. The 3T is fast but too stiff and twitchy to really be enjoyable to ride. The extreme short chainstay of the OPEN makes it really snappy and efficient but it retains comfort and controllability the be a fun all-day fast rider.