My searches turned up a little on each brand, but nothing comparing the two. I am getting ready to start building a 2002 WJ and one of the things I am determined to do is install a long arm suspension kit.
Both have great reviews and high user satisfaction, but both are quite different.

The Trail Forged uses a rectangular framework that welds to the WJ unibody subframe, creating mounting points for the 4-link and strengthening the unibody. But, it lowers ground clearance about 3 inches at the frame sides and all across the area of the framework. A flat 1/4" skid plate can be bolted to the underside of the frame, creating a flat skid surface to protect the transfer case. I really like the concept and execution, but wonder about the lost ground clearance. TF also uses square tubing for the lower control arms.

Iron Rock Offroad makes a bolt-on or weld-on kit with a cross member. It lowers ground clearance only where the lower control arm mounting points are and in the center where the cross member drops down for the transfer case mount. On the sides, the ground clearance is still as high as the stock subframe. IRO uses round DOM tube for the upper and lower control arms. They also have skid plates and frame stiffeners as other armor. IRO seems to be a little more expensive.

I would like to hear opinions about both setups. I really like all of Iron Rock's stuff, but I am really leaning toward Trail Forged's long arm kit.