Rain-x kinda cheats because you get to reapply every week and its thicker. It's sorta a temporary layer that washes free (washing the dirt away with the layer)
Klasse would do good if you did reapply every week.
But if I had to choose between the two, I would certainly choose Rain-x wheel stuff because reapplying
SG every week, would be a hassle.
One thing if you let you brake dust sit for 3 weeks (longest I've waited, but wheels were Klassed) it still comes off with ease.