I think I know what Cain is referring to.
In practice if one driven wheel has no grip, say ice or mud, the drive will not pass to the wheel with the grip, as it would with a plate type diff.
I have never rated this type of Limslip, for this very reason, for example, pulling hard uphill around a tight hairpin bend, the inside wheel will spin uselessly, but no power will be transmitted to the outer wheel until more grip is found on the inside, the very time an LSD would be essential I would have thought. Right Cain?
This is true, however (and it's a very big however) in most real-world driving the circumstances in which one will get absolutely no grip whatsoever on one wheel are pretty rare: yes, it'll happen on ice or slick mud, but really not very often unless one goes looking for it.
In all other circumstances, where there is some grip available, a gear-type LSD does very well indeed, certainly far better than an open diff, and it does so without the inherent disadvantages of a locking plate diff.
For rallying, or for track racing, a locking plate diff is what you need. For normal road driving, a gear diff is a better solution in my view.
