The compliance of the Tarmac. Yes, riding on beautifully smooth asphalt 100% of the time would be ideal, but for the those of us who spend our miles on chip-sealed, lumpy, or unpredictable roads (not just in training, but races too), the Tarmac offers real speed improvements. We all like to think of ourselves as somehow immune to these factors, that it can be just “pushed through,” but the Specialized guys even said it themselves - in real-world situations, added compliance leads to increased power and speed.
I added aero handlebars, Specialized RapidAir 26’s, and Enve 5.6’s to my Tarmac SL6. Is it as bleeding-edge aero as the Venge? Nope, but it isn’t that far off either, plus the added compliance improves power output and the ability to maintain a more aero position.
Both are beautiful, blisteringly fast bikes. Enjoy shopping! 