Is comfort is what you’re after then the B4 is probably the better choice for you.

@@bilsteinUS improved comfort and sport cannot be achieved both (by aftermarket damper) ? I heared people say monotube damper are superior, but I experienced that monotube damper was more harsh than twintube (on small bumps and at low speed)

Typically you are either after comfort or performance and as you lean further to one side of that equation, you sacrifice a little bit on the other side. A lot of times, the soft “comfort” that people feel is due to the lack of damping controlling the vehicle keeping it to the road, hence why there is increased body roll and decreased cornering performance. On the other side, increased performance (for example, a high end coilover setup for a track oriented vehicle) will be much more “firm” feeling as the increased performance and damping ability is keeping the wheels glued to the ground without introducing any body roll or sacrificing vehicle dynamics. In our lineup, the B4 will be the most comfortable if that is what you are after. The monotube damper will offer better damping performance over a comparable twin tube shock. But on the other hand, a twin tube will offer more “comfort” and a softer ride feel.