Alan, cheap replacement body panels are just that. It`t like a stainless steel spoon and a plastic spoon, they have the the same shape but one is much better that the other. The aftermarket getting a small scratch, rust will grow rapidly. Speed lines and door seams rarely fit correctly. Body men forced to use these parts spend excessive labor to get the fit up correctly.
OEM has the correct fit, has the coating layered onto the steel that resist rust, and are engineered for the best strength. Your choice, An exbodyman, Keith
PS Don`t forget to undercoat with a quality product. This will payoff at resale time.