MrFancypants
Autocross Champion
The criticism I've read about Bilsteins, particularly among the BMW crowd is that the valving seems weak on early impact and then harsh as the damper travels. So it's like it feels underdamped initially and then overdamped the further and faster it moves. Still, they're very durable and serviceable. I rarely, if ever, have heard of Bilsteins going bad in an unreasonable amount of time and if you can send them to be revalved to match a specific spring rate if you want to go with custom rates with something like a Ground Control setup.
Koni Sports on the other hand, seem to be less durable and fail more frequently (anecdotal observation, here's your grain of salt), but they are less expensive and Koni offers an excellent warranty. An additional downside is that it has been noted that the valving can be inconsistent from one shock to the next, as observed by those who buy these in large numbers and test them on shock dynos. The rebound adjuster offers some ability to tailor the ride and handling to your tastes, and as far as I can tell it seems that more people prefer the valving in the Konis both for comfort and performance. But another finding of those which shock dynos.... the adjuster is not terribly consistent, a half turn on one may not equal a half turn on the one you have on the other corner of the car. Another upside to the Konis is that they're just as serviceable as the Bilsteins, and you can get them revalved.
So really, they're both excellent choices, but you should know the strengths and weaknesses of each. IMO the downsides of the Konis aren't really all that significant in a street driven car, but maybe I feel that way because I generally prefer that brand.
Koni Sports on the other hand, seem to be less durable and fail more frequently (anecdotal observation, here's your grain of salt), but they are less expensive and Koni offers an excellent warranty. An additional downside is that it has been noted that the valving can be inconsistent from one shock to the next, as observed by those who buy these in large numbers and test them on shock dynos. The rebound adjuster offers some ability to tailor the ride and handling to your tastes, and as far as I can tell it seems that more people prefer the valving in the Konis both for comfort and performance. But another finding of those which shock dynos.... the adjuster is not terribly consistent, a half turn on one may not equal a half turn on the one you have on the other corner of the car. Another upside to the Konis is that they're just as serviceable as the Bilsteins, and you can get them revalved.
So really, they're both excellent choices, but you should know the strengths and weaknesses of each. IMO the downsides of the Konis aren't really all that significant in a street driven car, but maybe I feel that way because I generally prefer that brand.
