I would recommend the Rancho 9000s being that they are fully adjustable. In my experience when I sold 4x4 lift kits over the phone, people always wanted the best ride with their kit. I always asked them what they were doing with the truck in the way of accesories(winch, bumper, plow, etc. ), towing, off-roading, engine size and type as well as the climate they were typically driving in.
I typically only sold hydrolically charged shock as well as the gas charged or "Nitro" shocks. The "Hydro" shocks were obviously charged with hyrdolic fliud but they tended to give a much smoother, "Cadillac" ride and were recommended for lightwieght trucks like 1/2 ton rigs. However, they did not disipate heat very well, so they were recommended for mildly hot to cold climate conditions. And they did not hold up to extra weight put on the vehicle such as a winch or bumper. These accesories would usually cause a squishy ride with the added weight.
The "Nitro" or gas charged shocks tend to give a stiffer ride, are highly recommended for high temperature climate, due to the exceptional heat disipation and definately work well with extra vehicle weight. I usually sold the nitro shocks to people who have diesel trucks or the V10 engines since they are quite heavier than a typical V8 gasser. Also those who were running a snow plow, bumper or winch would benefit from these shocks because of their great shock absorbtion.
So that is my $0. 02, hope it helps in a good decision.
