I have asked this same question (well it was about my wife's ap noy my parent)and the response I received was if they are filed at the same time, then they both go to the Atl. office. If they are filed separately then the I-130 goes to the service center for your area and then when it is approved you file your I-1485 with the local district office ( not the best way to do this) It is much better to file them together. As you probably already noticed there is no posting for processing times for I-130's at the Atl. office, which means that you need o watch the times for the I-485 since they are traveling together.