Well, the detroit soft locker is a fully-locking mechanism which has its own beefed up carrier, replacing the stock carrier, whereas the Aussie locker is more of a drop-in unit that uses all the stock parts in the housing.
From what I've read, the Aussie locker should be considered a light-duty, economy locker, and is not meant for anything over 33" tires or regular, heavy abuse.
The Detroit soft locker is a complete carrier and locking mechanism, which has been proven to take lots of hardcore abuse and not complain at all. It should be considered a severe-duty unit meant to outlast the other parts in the axle. Its a buy-it-once-and-forget-it unit.
The bad part about this, is the fact that you'll definitely need a shop to set it up in your third member, whereas the Aussie can usually be done by the owner with just some simple hand tools.
Not trying to talk you out of doing the Detroit, I truly believe its worth every penny, knowing that I can hit any trail I want and never have to worry about it grenading on me. I'd much rather throw an axle in than try to pull the third to get it repaired when I'm out on a trail, miles away from civilization! But, they are expensive to buy and set up, that's just a fact of having one. I think if you pulled the third out yourself, took it to a reputable shop that's familiar with installing toy thirds and lockers, you'll be pretty close to around 900 bucks (~$500 detroit soft locker, shipped, ~$250 installation, ~$50 unforeseen extra parts, bearings, gaskets, etc).
At least its not an ARB! On top of all that, you need a compressor, plus all the wiring and plumbing to the diff! And the electric locker would be almost as expensive as an ARB! :wow: