If budget is an issue, I assume you'll be looking at lunchbox lockers. My research suggests that they are all pretty similar. I put a Spartan in front because the combination of the Ebay price and the rebate made it the least expensive at the time. The forums seem to like it and the Aussie (and Lokka), but the older ones (Lockright) seem to have served people just fine too. I thought the Spartan was really easy to install. Just get whatever you can find cheap.
If you aren't sure what you are looking at, be careful. There are folks who advertise limited slips as "lockers" on craigslist. That being said, if you need to drive it on snow and ice, a front autolocker will be better behaved in 2wd than a rear locker because they don't really lock when they aren't under power (which isn't to say they don't occasionally grab a bit). So, a good all-conditions setup is a locker in front and either open or a limited slip in back. In addition, if you've got a dana 35 in the rear, you might think twice about locking it, as it makes them even more likely to break. (And when you break a C-clip rear end, you are completely dead where you stand.)
Of course, if budget isn't an issue, ARB or Ox both front and rear! You can switch them off and on at will, but they are MUCH more expensive.
Paul