SuperBee, I wonder if your enviroment has much to do with your factors.
We must remember that besides the fancy names, clever marketing, etc.... carnuaba wax is in fact a wax.
My experiences have been the direct opposite of yours, but I don't believe it is because either of us is wrong. In Florida, it is hot for so long of the year and the sun is so direct (as well as the humidity) that it greatly effects the performance of most products.
Since carnauba wax becomes unstable at 170 degrees and melts at 181 degrees, we must remember that it softens at tempatures far less then this. In Florida, this means that anytime the car is outside (9 months of the year) the tempature is such that the actual wax is soft. This means contaminents can "stick" into the paint easier and IMO, are more likely to become embedded.
Again, this is me using a little fact to support a theory and I have researched it enough to back it up at his point.
But... I maintain a daily driven 550i, which recieved Zaino for the last year. 4 months ago the owner wanted to dry something different so we switched to
Meguiars #16. I detailed the car yesterday, and had to clay because it had so much contamination (more then it recieved in the entire year with Zaino).
IMO, Zaino is the best sealant I have used and among the best LSP there is, in terms of looks, protection, and durability.