All body shops use either OEM or CAPPA aftermarket parts for all collision repair on vehicles today.  There are supposedly no difference between the two unless the part is being ordered from an unauthorized parts resaler.  Make sure the shop you choose is getting their parts from a reputable CAPPA supplier.  This is a great first question to ask BEFORE you take your car to get repaired.  Most insurance companies will NOT automatically choose OEM and if they do, you will pay the price no matter what your body shop says, so understandng the difference can save you time and money.