I have more than a few miles with a multitude of diff options. I have personally owned rigs with open, clutch style LSD, G80, ARB air locker, electronic locker, and AAM's helical gear LSD. All of which where in 4wd vehicles.
They each have their own purpose, the selectables are best for everything. Open when you don't need the added traction, and locked when you do. Open gives the best snow/ice performance once your moving, as you don't have coasting lockup or lateral traction issues.
My least favorite was the clutch style LSD, followed closely by the G80. Both of them would "lock" the rear tires together when it wasn't good, such as coasting on an off camber forest service road covered in ice, all that does is make the truck slide. The also lock very easily on ice, reducing the lateral traction and inducing an unnecessary slide. I also found both of them to be pretty useless when added traction was needed. The clutch LSDs never had enough friction to transfer power and the G80 takes a big rpm differential with traction on one tire to lock (but does so on ice too easily). Many people don't realize what it actually takes to get a G80 to work, when I read the spec on it I was shocked.
Short of a selectable locker I was always a fan of open over a clutch style LSD. Under normal driving there was no difference but in slippery road conditions the open was more stable.
That was until I drove the helical gear style LSD in the AAM a axle in my Dodge. I have been overly impressed with its operation, mainly in snow/ice and in off camber situations. The truck tracks straight better than any other LSD, similar to an open diff, but when added traction is needed it's there. The only drawback is that they require vehicle movement to work properly, so they aren't so good if you are stuck.
That's my experience with many different setups. I prefer the selectable, but will take a helical gear LSD as well.
