This topic comes up from time to time, and since we do both spray painting & powdercoating in-house, please allow me to offer my opinion. Many people do not understand what the properties of powder paint is. The similarities of liquid synthetic urethane paint vs. powder synthetic urethane paint are very, very close. Therefore saying one is better than the other is hard for me to accept. What most people do not realize is, that there are huge differences in quality of powder just like there is a huge difference between Tractor Supply $30 a gallon brand of urethane vs. PPG's Concept $200 a gallon urethane. To some people, the Tractor Supply quality is acceptable for their vehicle.
I have attended several schools by my supplier and the second biggest reason for powder painted durability/failure is excessive mil thickness. I have shown several visitors to my shop where we have powdercoated aluminum foil, ...and then you can crumple up the foil, flatten it out and the powder still adheres. While I have not tried it, in all liklihood if PPG's Concept were applied thin enough, it would probably withstand the same abuse. If you were to have 10mil thickness of either product on the foil, it would likely flake off. Just as in sprayed urethanes, mil thickness buildup causes less durability. That means if many coats are applied in powder, there will be less durability but THAT is not how most powders are applied.
One other point that needs to be made, thoroughly blasting the wheels, osphos washing, degreasing, pre-heating, and slow baking makes a much nicer result when top quality powder is used. Cutting any of those steps allows for the price to be less but each of those steps cost money to do. Overlooking the fixed overhead costs differences between two 'coaters', there is no way these outfits charging $50-$75 a piece can do all of these steps and charge that amount based on my experiences..
