When I decided to go TJ to LJ 2 years ago but didn't want to start over, I got the opportunity to drive them basically side by side, with the exact same tires, axles, and shocks, because I literally took them out of the TJ and put them into the LJ.
The biggest thing I noticed was that it made the back end feel more harsh, like the shocks had gotten stiffer, because the weight distribution is more front heavy on the LJ. Even though the LJ is overall heavier, I'm convinced that the weight on the rear axle is actually less than an otherwise identical TJ because it's farther from the COG. Going along with this is that I had to get longer FRONT springs to maintain the same ride height as I had with the TJ, while the rear springs ended up a hair taller.
Second to that, I can feel more antisquat, when taking off from a stop there's more of a sensation of the rear end wanting to rise, rather than squat, under torque.