Assuming you have the good 2.5" to 3" lift package - springs, shocks, track bars, stabilizer, extended links - what would you gain from the additions of lower control arms front and rear? I have heard that the control arms on the JK are pretty good stock units.

 

Having adjustable arms allows you to set the caster and move axle forward on the front and pinion/center the wheel in the rear.

 

One set of arms will tilt the axle for caster/pinion correction.
Two sets of arms allows you to move the entire axle forward/backward in the wheel well.

Up front - As you lift higher, your caster gets lower and lower, and the handling becomes 'flightier'. If you can deal with it, don't worry about adding arms. If you hate the handling, get a set. (uppers are cheaper, lowers offer a better range of adjustability).

In back - 2doors with taller lifts may need to move the axle back. And if/when you replace the rear driveshaft, you will want a set of arms to adjust the pinion angle.

 

Good info. Thanks.