Definately install issues will bring you bad luck with any diff, locker, etc. But when you run across 100 ARB's on the trail and they are all working... Granted, there are the occasional line issues, or the seal housing (o-ring) going out and pumping diff fluid back up into the compressor (still an install issue, if you ask me, but I digress..)
For the BFE trip over the winter convention there was a guy in a black Cherokee that had the new style OX and they did not work. Second time on the trail with them. The first time they worked, then they were readjusted like supposed to be? Worked for a few then quit again.
OX is also not a stable company, and I wouldn't doubt it if they folded all together. With that, what good is a warranty if the company that made them is no longer around? ARB is very well established and I don't think they will be going anywhere anytime soon...
Small or large compressor? I think it's all prefference. I have a Kilby (York) OBA setup in my Rubicon. I'm installing ARB's in my D60 swap and I still am going with the large compressor, just for the ARB's. Overkill? Probably, but if it ever came down to it, I could plumb the ARB compressor and use it on the trail if my engine won't run or whatever. Also, a lot of the problems I have heard about with the ARB's leaking, the user was using an external type of air supply - not a ARB compressor. I wanted to take away that as a potential problem....
Definately, if you are upgrading locker and shafts, there is absolutely no reason not to go 33 spline. However, I beat mine up pretty good with 30 spline, 4.88's and 35's with no issues. But when you are talking about 30 - 33 spline axles, the axles are the same cost, but the ARB is more (~$20).
I've never ran/setup Alloy USA's R&P's, so I have no experience with them. As a company, they are great when it comes to warranty and support. Their axles are great. I don't see any problems running their R&P's? I do prefer Yukon gears and Alloy USA axles, IMO. Alloy USA carries some 4340's that Yukon doesn't is the only reason I use Alloy's axles.