Open headers vrs. full exhaust

I question wether the cutouts are as good as true open headers,I have seen other questions about this as well form racers.The few guys I know who unbolted their exhaust completely ran faster,but a couple guys who installed cutouts didnt see anything significant?.These were relatively fast cars-(11s to 10s)-Ive never ran uncorked becuase I drive to and from the track.