I own both a Domane Project 1 - Di2 Ultegra and a Emonda SLR Di2 DA. Both run same Continental 4000s11 x25 aired up to 95 on front and 105 on rear. Wheels are different, Domane has Bontragger RXLTLR and Emonda has DA C35. Emonda is 3.5 #'s lighter. I have cross checked all my Garmin data as I ride both bikes frequently averaging 400 to 500 kms per week. My average speed remains the same on both bikes with no noticeable difference. For sure the lighter bike is quicker on the climbs but my average week would see 1500 to 2000 ft of climbing, flat land here. That is best example I can give you that the Domane is not slower by design.