It's subjective. It depends on the person viewing it. What type of effect are you looking for? If you just want "great shine" and reflectivity, Zaino's probably a great choice for you. It will give off a great shine on any color, including the lighter ones which have much lower reflectivity than darker colors. This is why many people prefer Zaino for lighter colors.
I think I would use Zaino on darker colors before I would use it on white. Klasse has always done really well on white IMO. I've seen some good results with Zaino too but I think it is a draw when lighter colors come into play. On lighter colors shine is shine. It is really hard to tell the difference between which is actually shinier. Klasse with a P21S topper on it would look pretty dandy I think. You can get it for a little less than Zaino as well. If you really aren't going to be able to tell the difference anyway then you might as well save a couple bucks in the process.
I've seen Zaino on white, and it doesnt "wow" me, but I think that's hard to achieve with any wax or sealant on white. You certainly cant go wrong with it, and the finish was extremely slick. I say go for it.
i think you will be happy with zaino. It's reflectivity does wonders on white. I found the trick with white is to really detail black trim well and it stands out even more.
In my opinion, you can't go wrong with Zaino or Klasse regardless of color. If one does look better than the other on white, its not going to be extremely noticable.
IMO Zaino is great on white and sence you do not really have to worry about swirl marks as much on light colors I use Z2 almost all the time.This is my wife's Xterra not a great pic but to see it up close it shimmers.