Let me start with the higher the suspension frequency grip decreases. SO WHAT? Well this frequencey is a measure of how many cyles per minute or in a second, the car would go through and bounce up and down on springs alone. This matters greatly to you because the stiffer the suspenion is the less contact pactch will be touching the ground over rough surfaces, and if the tires in the air your not gaining traction or grip. The more grip your tires can make, the more force your putting into the car so you will need to up the resistance to body roll to keep it at an acceptable level. Race tires need a much stiffer suspension than a street tire. Cause their grip is that much higher and will cause the body to roll, losing camber and reducing grip.
In simpler terms...you want to run the softest springs you can get away with that reduces body roll to an Livable level, and has an approperate roll couple balance to give you the oversteer/understeer charateristics you want with the most grip your car can achieve.
"All springs "Bounce" its in their nature. Dampers Control the springs Occilations (bouncing). So if your car is bouncing, its not the springs fault its the dampers fault. To stop them from making the ride bouncy you need the proper damper (shock)."
That is why after a while with lowering springs your car gets bouncy if your on stock shocks. Much unlike common mis-belief Shocks don't just blow, it is a slow degreagation over time. That is why almost always older cars bounce down the highway if they haven't had their shocks replaced. It can also give you that FLOATY feeling on the highway over bumps, dips, and irregularities in the road.
"There's alot more to a damper then just the materials.... theres differences in valving, High shaft speed valving, Mid shaft speed valving, Low shaft speed Valving... Each one influencing different aspects of the damper. Low shaft speed valving deals mostly with how quickly weight gets transfered around the chassis, thus influencing the cars handling balance. High shaft speed valving deals more with how the damper deals with impats, bumps and such, so it deals more with the dampers Ride characteristics. Mid shaft speed valving deals with a bit of both. Tie that in to both Bump and Rebound differences.... and that gives you at least 6 different "tuneable" parts on a damper that influence handling and ridequality.
So you can see that the valving a damper has, not just the materials its made of, are very important to the cars ride and handling balance. (this is primairly why I don't trust those "cheep" coilovers... too little info dealing with the dampers)" And what is out there isn't that promising I have seen shock dyno's from both and Koni's appear to be the most performance oriented