That soft locker version is supposed to address some of the noise and harshness concerns that some folks have, Vaughn. I simply haven't had those issues, nor have I ever been in a vehicle with a Soft version. Tractech is a name I trust so I don't think they would make something that did not work. Call and talk to a tech guy. Go to some hardcore 4 wheeling websites. Those guys put everything to the torture test. Few here on TDR are truly hardcore 'wheelers by their standards. I know I'm not. I don't point my truck at a mountain of boulders bigger than houses and expect to somehow climb them like those guys do.
I'm a midwest mud and snow 'wheeler, and even then more by necessity (it was an obstacle between me and where I wanted to go) than by hobby (lets go out and see who can get the most spectacularly stuck and break the most parts).
A PowerTrax does require an open differential. If you have a factory limited slip, you will need to have an entirely different carrier set up with either a Detroit or a PowerTrax, so I doubt there would be much price difference.
The last Detroit I bought was for my old-style K30 Chevy with a 14 bolt open carrier. Those usually sell for about $300 these days while most other Detroits were (then) about $600. I actually bought my drop-in unit new-in-the-box on ebay for $250 with shipping. Price varies quite a bit depending on the axle since they have to make a whole new carrier except for the 14 bolts.
JD is right. You really need to know exactly what your axle spline count is as well as your gear ratio before you order. The best way is to count splines and teeth, imo.
Lockers are "low center seeking" on very slick surfaces. A spinning tire offers near-zero traction and can as easily go sideways as forward. The same holds true when braking for a locked-up and skidding tire. They can go any direction.
Trust me, I have had to literally outrun many semi trailers, singles and doubles, that I was pulling on ice in order to drive out of a jacknife! A trailer with locked up brakes can and will pass the tractor! that is why empty trailers are so dangerous. The brakes are designed to stop heavy loads and they (too) easily lock up the wheels under even the gentlest brake application when there is no load, especially on wet or icy roads. One of the hardest things to do when life turns to crap on ice is to deliberately apply more power and speed, but that is what you must do to get the trailer(s) back behind you sometimes.
Anti-lock brakes were designed specifically for this reason. Too many folks do not know how to drive without them and are too reliant on them these days. Not me. When they work right, they are great, but they tend to take away too much control sometimes.
Again, just like driving with a locker, you simply need to be aware of how your vehicle drives and stops and handles under every condition and drive accordingly.
With an open diff on ice, you have one tire spinning and the other stationary and acting as an anchor and resisting sideways sliding. It isn't helping to propel your vehicle, but it does help limit sideways sliding a little bit. This why you will hear some guys (not me) claim that an open diff is better than a locker on snow and ice.
If you apply too much power to a locker, or limited slip, on icy surfaces and get both tires spinning, the rear-end of your vehicle will slide wherever gravity and momentum takes it. Don't blame the locker. Learn to control your right foot and simply don't DO that!
Remember: Most handling problems can be traced directly to the nut on the steering wheel, brake pedal and throttle!
Of course, on ice that slick, even an open diff cannot stop a sideways slide on a an off-camber surface. Ice is ice.
This all holds true for hillsides, too. If creeping around the slope of a hill, keep your power under control or your rearend will slide downhill. Having an open diff does not guarantee the non-spinning tire can or will be able to hold the vehicle either.
I like all the control I can get. With an open diff or limited slip you have NO control over which tire(s) drive or spin or when. A Detroit guarantees both are being driven all the time.
As you pointed out, you must learn how to drive a locker. It is a great tool, but it is different and you adjust your driving accordingly.
The truly tough old Chevy's with 14 bolt rears did not come from the factory with "limited slips" to the best of my experience. They DID, however, frequently come factory-equipped with a LOCKER. It was called the "GovLok" and was a more complex design that involved internal flyweights (governor) that sensed wheel spin and locked the diff. And I do mean locked. They sometimes are accused of being prone to breakage, but I had one pickup that I drove for many years that had one and it worked about as good as a Detroit and never gave me any problems.
That proves that GM was not afraid of the handling characteristics of locker-equipped trucks. Check out most any surplus military Chevy and you will find either a Detroit or a GovLok in the rear 14 bolt. they were standard equipment on military vehicles because they WORK and are reliable.