[andino]

I'll add my anecdotal experience to this using a KW V1s and Bilstein B14s on my car. These are all in the context of xdrive for F31 since that's what I drive.

KW V1s have a specific kit for f31/f34 which use. I found the ride quality of the V1s quite nice. The day to day commuting with them is comfortable and there's not much see-sawing. Where I didn't like them was when I was deep into a corner and they began to feel a bit under dampened. This was the primary reason why I sold them and switched over to Bilsteins.

I currently run Bilstein B14s. This setup makes the car feel much more lively but at great expense to ride comfort. Bilstein uses a single part number across all f3x cars only differentiating by xdrive or sdrive. This means that the rear spring is under sprung (as Farkie mentions in his post) and my car has a pretty poor ride when the bumps come continuously. Basically, it'll feel like I'm see-sawing quite a bit over my KW that I'd replaced. The benefit (and why I still run them now) is that the b14s feel much more planted in turns and under spirited driving conditions. This is likely to them being much more dampened compared to the KWs.

I only know the ending for the rates for the the bilsteins so its hard to say how they compare to the KWs. At some point, I'll be handing them over to a suspension tuner to get them dialed in for my car. I did find that running an eibach spring equivalent to almost the f80 ZCP up front with an adaptive damper vastly improved my ride so I may end up changing out my spring setup for different ones to improve the road going characteristics. It really depends how the car feels on track after I get some time out there.