Personally i have only had experience of the KWs, and to be honest the build quality is second to non.
so far i have run Kws on all of my cars and they have not once let me down, and the ride has all wase been firm but well controlled, i wouldnt say that there too stiff for road use either, i like them
the only thing i would say that lets the KWs down is the adjustability of them, the rear bump adjusters are fiddly to adjust, and also if you want to adjust the rear rebound you have to drop the topmount (2 bolts) to be able to see them
I have the clubsports on my car now, but i have had them apart to set the damper lengths properly for how low i wanted to run the car and have also altered the spring rates too, they are firmer than the usual clubsports now but considering i live out in the fens i still wouldn't say there spine braking stiff
It would be good to hear about the Bilsteins tho