Maybe Sullivan held onto the ball longer trying to extend and make plays, hard to say unless you see the video as to what was going on.
His high completion percentage combined with high sack rate appears to show that he doesn't throw the ball away, and eats it if he has to. His shorter yards lost per sack indicates he may have tried to scramble and run several times but was tackled for a loss, which is counted as a sack.
I do agree Sullivan is a much better option than Hill.