Hey Dan, as you can see, everyone is recomending what they are running (except Paul). I'm running a Detroit, and that's what I recomend.
Here's how I look at this subject. If you want absolutely no hassle reliability and performance and are willing to live with tight steering on occasion......get the Detroit. If you are willing to live with the potential for locker malfunctions (internal seal, external fittings and hose, solenoids, etc.), and with turning the locker on and off regularly, and you are not willing to live with tight steering now and then.......then get the ARB.
Remember though, that many of the times that you're in a tight spot on the trail, you are also in the middle of an obstacle with your locker on, so it makes no difference whether you have an ARB or a Detroit. I use 2 low often, and nearly all of the times that I make sure I'm in 2 low to be able to make a tighter turn, it's on a relatively easy section of trail where I just don't want to bother backing up. Now, I really, really like my 2 low. If I had an ARB, I might really like it......except for the fact I'm part of the group who wants absolutely reliable performance and I'm willing to live with a quirk or two. It's a very personal thing.
Now get the Detroit, get the Warn shafts, and get out to JV in the fall.