Lower control arm question

I've got a 98 4.0 that I'm in the process of piecing together what I need for a 3" lift. I think I've got about all I need, or at least it's in the mail, but I was wondering about control arms. Some of the 3" kits come with them, some don't. What's the deal? What happens if I don't pick up a pair? What are the benefits if I do? What is the advantage to using the WJ arms? Thanks in advance-

Biggest issue is keeping stock geometry. The kits that come with the arms are trying to keep stock geometry, the ones that dont have them dont think the change of geometry and axle location is significant. It also saves cost to not include them. If you dont get them, the axles move a little which changes steering geometry and wheel base. It is certainly doable without, otherwise those kits would not be able to sell.
Not sure about the WJ arms question.

anybody else have thoughts?

I'll throw in my .02

are you going to use this as a DD only, or a trail rig only or both?
DD only, you can get by with the stock arms. Suspension geometry won't be the same as stock, due to the shorter length, but the difference at 3" is marginal. Strength wise, you should get some tubular lowers for a 3" lift. If you think you may want to go bigger down the road (we all do) look into some adjustable arms.
The factory Jeep control arms (TJ, XJ, ZJ) heck- even the fullsize dodge trucks- are junk stamped steel, and not very thick. They are ok for street/ highway use, but they are very vuneerable to damage off road, which usually results in them bending. I had a 3" skyjacker kit a few years ago, which included new lowers. They were fine. However- if you are going to wheel this thing much- I did then, and still do now- keep in mind that the factory arms (lowers and uppers) have their limits.

Sorry for the long reply- I hope at least some of it answered your question.