I would think that this is going to depend on how you are going to use your rig, such as Rockmonkey has already stated. If you are wanting to run your rig in the snow then I would suggest a selectible locker would be best, you may want one anyways. Lots of advantages to an ARB or OX lockers. I run a detroit in the front for a couple of reasons. First, stout, it is a tough SOB. Second, easy to find and set up. Third, simple. Forth, cheaper than either selectible locker. No lines or cables that will leak or need adjustment. A front spool would also follow these same guidelines but would be even more simplified. When I do run in the snow I just get out and un-lock a hub. Kind of a pain to get out and lock and un-lock but, for me and my rig this is the best way for me. This is just my .02.
LT.