I've had both on the same vehicle. The Bilsteins were gas charged so there was resistance on even the smallest road joint/bump that I could feel through the steering and in the coach. The Koni FSD's are NOT gas charged so they gave me a much smoother ride and absorbed the smaller bumps.
As far as big bumps and rough roads, they were both about the same.
Since I traveled mostly on smoother paved roads, I preferred the Koni ride to the harsher Bilstein ride.