I have used Sonax shampoo and say it is a good shampoo, compares with P21S but I think P21S offers little bit more slipperyness, is that even a word. Both great shampoos but I think
Pinnacle BodyWorks Shampoo is better than both in terms of performance. The cost is a little bit more, but not much once you break it down to per wash.
I am sure someone else can input on this I have only used P212S and Sonax once a few months back.
As for the
Meguiars Gold Class, it is my main shampoo, does a good job at a GREAT PRICE. $10 a gallon from Target and I am pleased. Bought my gallon a few weeks ago. Very good shampoo for family cars, that need to be cleaned and pmapered a little bit, but not as much as P21S, Sonax, or Pinnacle. It is in no way inferior!
happy detailing
Jason