The difference is between simply slowing a wheel that is spinning (the braking action of the traction control system) and transferring the torque of the wheel that is spinning to the lateral wheel that is not spinning. Forward energy is lost with the braking, while it is transferred to other wheels with traction with the LSD.
As for the implications of this, it depends on the situation. As the poster above said, it may not be very useful under certain circumstances--snow and ice perhaps. But, an important thing to remember is that the LSD does not hinder the traction control system that works with brakes. That system is still free to operate, which means that if you are in a situation where the torque transfer to the lateral wheel with traction (by the LSD) actually causes it to slip, then you still have the braking action of the TCS/ESC. The LSD is not a substitute, but an additional feature.
As I've mentioned before, the LSD is not exclusively and off-road feature. Sports cars, for example, rarely come without them. Torque transfer to an outer wheel in a curve, if needed, provides stability while maintaining forward momentum to a degree not possible with the simple braking action of a stability assist system.
As for potential issues with the clutch in the LSD, obviously, the more you use it, the more wear it will get. But, my sense is that LSD technology is well-established and longevity is not the problem that it might be with other "added features." A completely new ELSD may have some electronic issues to be sorted out, but hopefully that could be done with software updates, which aren't invasive.
I'll say it again, even the base QTI should have LSDs. They are a safety feature, and they enhance handling, even if you never go off-road.
2011 GC Limited 4x4; Blackberry Pearl w/ Light Frost Beige; 5.7L HEMI; 20" Wheels; Tow Group IV; 730N