The clayton setup is a "mid arm" suspension. It is definately a nice upgrade to any shortarm. It will perform slightly better during articulation, climb significantly better, and handle/ride significantly better then a quality short arm.
The short will definately get the job done, and is a good suspension as well when done right. Specially if you stay 2-3" with the lift.
4" and more on SA's dramatically effect the handling, ride quality, and climbing performance on TJ's.
Also, if you are using full size johnny joint lowers, its very easy to just weld in a set of clayton brackets down the road and build some lowers using your existing JJ SA's. You either build new links, or stretch your originals.
Joints are the most expensive component of any suspension. If you already have a full JJ SA, done right, you can custom mid arm it for WELL under 1000$ in parts.
Lowers tubing is 10/ft. You only need 10 ft.
Uppers tubing is less then 5$/ft, and you need about 9ft.
A full bracket set from clayton, meaning front and rear frame brackets, rear link bridge, and front link bridge is less then 500$. Probably 550 shipped.
So 150$ in tubing, 550$ in brackets, the use of your existing SA components and you are set up on a full custom mid arm suspension.
The key is using good stuff in the first place that you can continue to use down the road as you upgrade.
That way you can build in stages as money allows, but not lose your shirt selling an entry level suspension you bought for pennies on the dollar and then turning around and paying full price for a whole new system.
Lots of options, but my main point was to make it clear that the RC lift that caught your eye really is not quality suspension for dollars spent.