Heck, I dunno. In my pre-Autopian and early-Autopian days I used the Armor All Detailer's Choice spray...which wouldn't last thru a wash or a rain, whichever came first. Then I bought a bazillion products, but I never bought Zaino because of the zealotry of all those guys who went to DClub. Then my mother bought a new car that I thought I should take care of, but wasn't going to be able to do it regularly, so I took the Zaino plunge for that, and that's the only car I use Zaino on, so far. The Z-16 seems to have a fantastic life on her Goodyears, but it could just be the tires, driving habits, etc. FWIW I have the original Z-16, not the newer, thicker version. I don't use the greasy-kid-stuff dressings simply because I don't like the mess.
Maybe I don't get the tires clean enough, maybe it's the tires/weather/brakes/driving habits/washing frequency, but the other dressings I have used don't seem to hold up well enough to not be reapplied after a wash.