Posi-lock cable is used to replace the vacuum switch assembly that was stock for engauging and dissengauging the 4wd mode on the front axle. I am assuming you are asking if the Jeep will handle better if you install a locker in your front differential. I think the answer is "somewhat". What do have on your Jeep, now? in regard to lift, tires, etc. Apparently, you have a locker in the rear differential. Do you air-down your tire pressure when you're four-wheeling in the dirt? Airing down the tires to between 10 to 15 psi will allow improved traction, and perhaps improved control, less bouncing, improved ride, etc.
BTW, have you noticed that many PC's today come with additional keys, such as: commas, periods, question marks, etc.! <img src="/forums/images/graemlins/lol.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" />