Well, if the question is lock-rite vs. no-slip for the 8.25, you have to ask what year it is. If it's a 97+ XJ, then you have no choice but the no-slip, since it's 29 spline. If it's 96 and older, then you have no choice but the lock-rite (although I've heard rumors that some of the "classic" 96 XJs that were at the end of the year may have 29 spline axles. this may be a rumor, or maybe just a jeep thing).
The no-slip is a little smoother than the lock-rite. The aussie is smoothest, and was designed by the same guy who designed the lock-rite, it's just different material and slighlty different design, but basically the same thing.
On the trail, they're all the same, all 3 of them work.
Like someone already said, if you're on 33s and stock gears, you may want to wait to regear and get a full detroit or arb, or electrac or whatever your wallet will afford you, but I think we all understand you're wanting a locker NOW! That being said, I got a great deal on a lock-rite for my XJ from a guy who had it in his XJ for ~2000 miles and then decided that he needed to go with bigger axles. My friend got a great deal on the locker he had in the d30 too!!! If you've got money, and like to be generous to those of us who are still in college and can't afford a brand new locker, by all means!!
Oh yeah, the ratcheting isn't that loud. it only happens when you coast around turns, and all of them do it. If the noise is a serious concern, you probalby shouldn't be thinking about a locker.