How about this: "In a class based model, skeletal templates (classes) serve as object factories, with something general (the class) serving as the starting poi

How about this: "In a class based model, skeletal templates (classes) serve as object factories, with something general (the class) serving as the starting point of something specific (an object). In a prototype based model, the prototype object provides a fully fleshed out starting point for other objects, with something specific (the prototype) serving as the starting point of something even more specific (the inheriting object)"