What is the difference between a Primed bumper cover and a Polyurethane bumper cover?

What is the difference between a Primed bumper cover and a Polyurethane bumper cover, I don't know which one is better to buy. Thanks in advance!|||Both are the same. Either would need to be painted to match the vehicle. They are never sold new in the correct color. New bumper covers must always be painted. You also use different paint on the bumpers. The same paint used on the body will crack. Either a special paint is used or sometimes an additive is put into the paint to make it flexible so it won't crack.|||The primed bumper has coat of paint primer on it. It still needs to have the final coat of paint to match your car.