An aftermarket coilover by almost ANYBODY is going to have a superior shock. GM gave us a choice of a dozen spring stiffnesses, and we're stuck with only ONE choice of shock.
Took a lot of testing and tuning to get something in the rear to match the Z71 springs, but we never had a choice in the fronts.
With my Icons (RIP - I may never the mounts remachined if this work situation keeps up), I could run on desert washboards at 2-3 times the speed of the aftermarket Bilsteins. Stiffer springs helped a LOT, but the shocks were instantly noticeable. 2" rocks, 3-4" washboards, and the occasional 10" whoopsie would just disappear. You also need to be aired down, and there aren't a lot of empty and WIDE washes that you can do this in, but Split Mountain Wash is where I did a lot of testing. Stock you'd be limited to 5-7 MPH. With a lift and stiffer springs maybe 10-12. WIth my Icons at their best I could do 25-35 and everybody would eat my dust and die trying to keep up.
Where I broke the Icon mount was on a lumpy but not rock-filled hill climb on Palomar Mountain - dried washed out dirt fire road - where the suspension would alternate from fully compressed to fully extended every ten feet. Used to climb this at 2-3 MPH and I was probably doing 13-15 when it broke on an extension.