What makes a better paint? Do more expensive paints contain more durable pigments and resins?

Yes they do. You hit on some key items that improve the quality of finish. The resins along with the binders give you the quality of finish. Also, the way the product is produced can impact the quality. Paint goes through a piece of machinery called a ball mill. This grinds everything together. The size of the balls used and length of time it goes through the mill impacts the fineness of the pigment grind, which impacts the quality of the product.