Some auto makers put super soft springs (seems mostly for the US market for some reason) compared to cars for other markets.
I think U.S. got used to limo style soft rides and expected that soft feeling even in small cars.
While soft is nice , too soft suspension can cause handling problems if there are geomotry changes with suspension travel. (which is the norm)
A car like this then fitted with what I would call normal stiffness springs can improve its on road performance dramaticaly., and if the spring maker did a good job at estimating the needed stiffness the ride shoudlnt be too bad either.
What is of concern is that some of the cheaper spring makers dont do much testing of their products , so you can actually get a handling package which is unsafe, especially when excess lowering is involved.
i agree with your points and often suspension setups designed for racing are very unsafe on the roads because they are too stiff and offer a steering bias that is unfavorable on public roads. i think we agree.
my point is that mildly tuning the suspension (properly) can improve the safety of the car as long as the driver knows how to work with it, in rebuttal to compaq888's post.
don't waste your time or time will waste you
I would first ask, how much weight are you going to put back in the car? I keep 100 pounds of stuff in the back of my car nearly all the time, so do I adjust the suspention for when I have the weight, or not? the extra weight is alwas going to be in the rear, and haveing the rear a little high is better then having it to low, I would pick that worst case hight (100 pounds of cargo) and leave it adjusted there.