Ok I will shed as much light on this topic as I can, I'm actually surprised you guys havn't mentioned any of this info.
My vs in my avatar is the car I gained this experience with.
First of all, Kings vs Pedders (things may have changed since as my experience dates back 5 years)
I have owned both and my personal opinion is kings win hands down, there is just no comparison. Now this may not be the case for everyone as I like my cars real low. First I purchased pedders springs and shocks, as low as I could get, When I picked my car up from full install I thort has it even been lowered?
It was lowered but just not to my lowness. ride was reasonable but very firm. I had both shortened shocks and springs in and hated it.
I decided to do some research and this what i found. Kings do a much more ride friendly spring then pedders, only when you install kings (generally) because of the softer rate you will find your car will be riding on bump stop more.
I purchased a set of v6 Kings SSL front and rear. Once installing them I realised that pedders lowered front shocks are no different in length to standard shocks and rears were only marginaly shorter. This in turn didn't even keep the pedders springs I had captive and when I installed my kings SSL they were no where near captive when car was fully lifted. now with kings SSL all round and pedders shortened shocks all round it rode like a bucket of bolts.
After much more research I discovered it was not the springs that was making my ride so bad, infact the front shocks lasted around 5000km. I made alot of phone calls and the only front shock i could find that was actually shorter in length was an Ultima shock. After purchasing these and installing them, my springs were 98% captive and ride was un believably good. After replacing 2 sets of sway bar bushes I also installed a Whiteline Adustable sway bar.
Now to the rear. I couldn't find any brand that made a shorter shock than pedders so I stuck with them. The rear was still riding very ruff as it was basically sitting on bumpstops, first I removed the bumpstops and went for a drive and was so suprised at how smooth it rode. So I shortened the bumpstops as much as pactical and re-fitted them. After this I was able to remove both upper and lower spring rubbers and still had a smooth ride. Still smoother than it ever rode with pedders springs and shocks in it.
Just my personal experience, but I hope it helps some one wit there experience