The purpose of this study is to demonstrate that the safety and effectiveness of the Medtronic Transcatheter Aortic Valve Replacement (TAVR) system as measured by rates of all-cause mortality or disabling stroke at two years is non-inferior to Surgical Aortic Valve Replacement (SAVR) in the treatment of severe aortic stenosis in subjects who have a low predicted risk of operative mortality for SAVR.