The detroit is hard to beat. If you do hard wheeling/crawling (where one wheel might be completely off the ground), a true locker or spool is the only tool for the job. My detroit has over 60k mi, and has held up fine. But the street manners are a bit rude at times. The thing pops and bangs on the street and on the freeway, if you lift off the throttle, you might only have one axle locked and it tries to change lanes. Just some nuances to get used to.
An alternative you might consider is a trutrac gear posi. I've run that too in the rear, and it will do 90% of what a detroit does, and it behaves like an open diff on the road. Add a spartan in the front, and you'll likely never have a problem in snow or mud. Its only when you hang a wheel in space that the trutrac will spin. Adding some e-brake was usually all it took to keep moving, though.
But like trever says, it depends on your usage. If you climb boulders, lockers are the way to go. And I personally would stay away from the clutch style posis. Unless it was in good shape and free!