There are three different type of selectable lockers out there, Air, Cable and electric. Their are pros and cons to each, Air line separation, o-ring failure inside the differential, cable seize up and cable breakage in and/or of the differential, broken electrical lines, and electrical activator malfunction inside the differential. There have been a few reports of shorting out in the E-lockers as well, but I have never seen this happen.
Each locker has its risks of breakage. Good activator line running will solve most of these issues. And good maintains will also.
I personally run dual ARB's and have for 4-5 years with no problems. I have never pulled a line while off or on road for that matter. But with every other critical part on the jeep I carry spare air line and repair fittings. And both front and rear o-ring kit just in case(never had to replace the o-rings either). Just like one of my friends carries two spare cables for his OX lockers, although you do have to open the diff cover to pull the broken end and replace the new cable.
No one in my group has an E-Locker, so I don't know the particulars of it.
The only issue I ever had with my ARB was I broke a rocker switch cover, loose pepsi can, and had to use a pen to turn it off and on (7.00$ to replace the switch cover, carry spares of them now as well).
For the money selectable lockers are the way to go if this jeep is your daily driver, especially in the rear axle. I have seen/felt the driving manners of a Detroit locker on snowy pavement before. The owner was used to it, and didn't even flinch when it locked up on him, I on the other hand didn't like this feeling and chose a ARB.
The best way to know is to ask any of your club friends who have lockers and ask them for a test drive so you can feel how they handle on and off road. How hard it feels to lock in (cable). And costs assoicated with it (Air).