Ive been watching this topic for a while...
the actual power stabilisers have nothing to do with earthing, so in fact you are only comparing the quality of cables. Good quality cable from an electronics supplier will give you very similar earthing results. Another thing is that if the car already has a good earth, the kit will not provide a huge difference, but for older cars with poor earths it will be beneficial.
the powerstabiliser box smooths out votage fluctuations, which can help with starting and ICE. you may not even see an increase in votage tho.
in my opinion the PIVOT one is not worth it, they are relying on people to buy for the brand, I have done alot of research into these and have used similar systems on RC cars in the past.
I have built my own power stabiliser, for around $25 you can make a quite decent one that is compareable or the same as alot of commercial ones, the pivot one may be the best but imho it is not $75 better. I was planning on selling these but I did not want to supply a product that produced such a small performance gain, and testing on my car did not convincingly prove that it provided a noticable result