The difference from a short or factory length control arms to a long arm kit its like night and day. The main reason is that the pivot point of the axle is pushed back allowing the axle a lot more travel along its arc of movement before transferring any of that energy into the frame rails as a lifting or falling sensation or a bump movement.
The best way to experience it without riding in one is to take a basketball and with arm held straight down and bending your at the elbow only. Bounce the basketball. Now held your arm out straight, using the whole bounce the ball. You get less jarring from the ball with your arm held out straight because of a bigger arc, and its ability to adsorb the impacts.
But if it so much better why didn't Jeep just go with this? The cons to this lift, yes there is some. First off your comfortable riding shock that you now enjoy might not be up to the job of handling more of the axles weight and movement. And yes your springs come into play a lot more. A lot of the complete kits come with new springs, but many don't take into account of the amount of research that went into it selecting them. You want a longer spring with a progressive rate since your going to allow the axle more movement up and down and stiffer so the customer doesn't have to buy a 200$ race inspired shock to dampen the small amount of road vibration transfered back to the frame rails that el cheapo shocks couldn't handle not having the right valving to handle the quick fluid movement.
If you plan on going to this I would recommend that after you bolt on this kit you find a local shop that knows how to weld parts to the frame rails (auto repair shops are your best bet here) and spend 25$ or so and have them tack this bolt on kit to your rails. I found mine starting to move less than a year after it was bolted on to mine. Second is you start looking in some bone yards for a grand Cherokee, on the front axle of some wranglers and most Grands is a small clip that holds the coil spring into the base pocket on the axle. My 2001 didn't come with this clip but a hole and location for it. (Will send pictures of it later). I found that without running limiting straps I could drop my front axle far enough that my coil spring could unload itself and turn in the pocket damaging the first coil. I have since added different springs, shocks, and put in these 5$ little clips.
With my old crew in Utah I had the opportunity to ride in short arm jeeps and different long arm equipped jeeps from different manufactures and each was a different ride. From low budget to top end kits from Fab Tech to Tera-flex's LCG. Each had its pros and cons but a smoother ride than factory arm lengths lift kits.
On the whole I found I can wheel harder and take the whoops a lot faster that most due to my jeeps long arm kit ride. I hope this gives you some incites and makes you go with this mod, it is one of the biggest mods I tell all my friends to do, the ride there and back is just as important as the trail ride itself.
