17 Oct 2010 at 15:57 - 7
A Superior Salvage Kit is the same as an Expert Salvage Kit, it just has more uses and costs more per use when purchased from a vendor.
You want to use an expert/superior salvage kit when you want to take a magical item off of a weapon/armor (though it has a chance to break) or if you want to have a chance to salvage rare materials from the item. If you use a regular salvage kit, you will always salvage common materials only. e.g. Use an expert/superior salvage kit on a sword, you have a chance to salvage either iron or steel. Use a regular salvage kit on that same sword, and you will only salvage iron.