Technical difference in the braking system. When I first flown this "newer" aircraft, our engineers called it "brake-by-wire". The difference is mostly transparent to the pilot.
Another interesting aspect to it is that for NO ANTISKID it is not necessary modulate pressure manually to 1000 psi, system takes care of it.
I always thought that this new braking system is fitted to aircraft with NWS on the Y HYD, I would be happy if somebody better versed could confirm or dispel that.