My view on piston coatings in general is snake oil. If its a race engine getting tore down in each season have at it. But for anything else its a waste of money. The coating will wear off and ends up in your cylinder or crankcase. Your run the risk of clearance and increased knock or slap over time as it wears down and get uneven heat buildup. The thicker the coating the more risk as it wears off so a thin coating may actual be idea. I have never used a coated piston nor would ever get one for my applications.
A top coat provides a thermal barrier to keep heat in the combustion chamber, and no it does nothing to keep it cleaner and prevent carbon buildup. Also to note, as the coating wears down you will have areas where the piston is absorbing more heat which can cause distortion in the piston.
Another good point. I would want the pistons and cylinders absorbing as much heat as they can and evenly as they can and let the fuel and coolant absorb the heat out of the block, heads and combustion chamber, like its supposed to.
My bottom line if your looking for longevity skip the coatings and get a quality 2618 piston, and if your running higher compression and lift do 3v specific valve reliefs, that's my opinion.
