I also like the fact the rear exhaust vents on the X-Fourteen are always open. On the RF-1200, there is a horizontal slider to open and close the rear exhaust vent, but I honestly have a hard time feeling any performance difference. You also can not visually see if the exhaust vent is open or closed.
The other noticeable bit of airflow difference is air coming up into the helmet from underneath. I actually had a contact lens get blown out during a track day in my old RF-1000. The X-Fourteen has a lower chin deflector which does a good job of preventing air from curling up under the chin compared to my RF-1200.
Of course, the big marketing point of the X-Fourteen is all the aerodynamic work put into the development of the shape of the helmet. I can tell you that even at highway speeds I could feel the added stability from the extended rear profile and flaps. This was especially noticeable when my head was turned a bit. I’m not quite sure how to describe it aside from the helmet just stays put on your head. There’s none of the buffeting that is common with helmets when at speed.