Now I have tested time and time again, all sorts of different springs from all kinds of manufacturers. I am always pretty confident with the swift product. Now if I find a better product then I will back that, but so far to this day I have not found one.
Now Zerosum brought up a good point. What you claimed is the exact thing that splits the Swift springs apart from all the other spring manufacturer. Now lets say I were to get the most precise spring from Hiperco or Eibach and compared it with a Swift spring. On a spring dyno it will be very similar. The graph would probably look identical, but then if you were to physically use those springs and swap them out, to use back to back, It would be a night and day difference. You would immediately be able to tell which is Swift. The Swift will feel much more compliant, in fact its exactly what Zerosum said "the impacts are much better damped". I know it is hard to understand but I will explain.
It is not the spring rate that distinguishes the differences in the impact of uneven pavement. Spring rate has more to do with the reaction of the amount of force put onto the spring. In other words to put it in simple terms, it will affect body roll. I am not saying that initial impact of uneven pavement can be softened by softening spring rate, but that is not the correct way to make a car more compliant. The correct way is the shock absorber the main reason for this is because there is a form of mechanical lag with the spring. This is why some suspension companies do not even believe in adjusting spring rate (talk to the techs at KW).
Now for some reason the reaction rate or the time to respond from impact with the Swift spring is much much quicker than ANY other spring company. This is something that can not be seen on a spring dyno. But can be tested. In fact through the testing that I have done we have seen that even with the exact spring rates being used the tire temperatures with the Swift springs is always cooler. This is the reaction rate of the spring, or frequency of the spring is what some suspension scientists explained it to me as. (LOL)
But of course track testing is nowhere near accurate for testing because there are so many different variables that come into play with simply measuring tiretemps.
Anyways the reason why we came to the conclusion that the reaction speed is different is because we ended up taking the car to a shaker rig. Which is an extemely expensive process, which I obviously did not pay for but was there to help figure out why the Swift springs were so different.
Anyways what I am trying to say is that the Swift springs even with the same rates will durastically make a difference with the performance of the vehicle.