I never used Zaino, seems to cultish for me and the people that use are very defensive so I won't say anything about it, but I've used Klasse AIO and SG for many years and I always liked it until I tried Meguiars NXT Tech Wax. They have similar properties in terms of fillers, cleaners and shine but NXT is way easier to use as you can do the entire car, let it dry and quickly wipe it off whereas Klasse AIO requires a moist applicator (which dries quickly in the summer) and you have to do a section at a time, let it dry just enough not to much, not to little and it doesn't come off that easy so I feel I can wax a car with NXT in half the time of Klasse. Klasse SG to me is worse as it streaks so I stopped using it. The advantage that Klasse has is that it does last a little longer. This is where #21 comes in, has similar properties to NXT but doesn't have the cleaners but lasts longer than NXT or Klasse. Having said all that, nothing comes close to Meguiars #16 in terms of shine and long lasting but doesn't have fillers or cleaners so the paint has to be in good shape to begin with, too bad they pulled it off the market.
I know Meguiars makes some products that are not that great, some are pretty bad but their professional and detailer line has some great products, it's a shame they don't sell these to consumers like #21 or their polishes like #83. The only downside to the pro products is they only come in larger containers.
