I don't think the suspension is any different - at least I didn't see any mention of a difference on the Jeep website. If you're planning on lifting, I'd strongly recommend a Xterra. It's got better axles, far more ground clearance, an actual truck frame, and you can fit bigger tires.

As far as actual ground clearance goes (as opposed to mfg #'s), I saw on a jeep board that guy's with a 2.5" lift on pre lowered KJs (so 3.5" over current stock) with 31" tires have about 10.5" to the front diff. My X just has a torsion crank and 32s and I'm in the 12.5" range (off the top of my head) up front. Also, the LCA's on the KJ hang very low at least a foot in from each tire - and they're more in the 6" range.

On the plus side for the KJ, I think they are somewhat cheaper to lift.