This is a common source of confusion. No, you do not have a choice. Employment based I-485s must always be filed at the Nebraska or Texas Service Center (depending on where they live). Family-based I-485s are filed at the Missouri Service Center (via a Chicago mailing address). And if your I-485 is asylum based, you must always file at the Nebraska Service Center, no matter where you live. For detailed up-to-date instructions, please view the
USCIS Web Site.