the bolded parts are why I say he isn't comfortable on the ball, of course he isn't bad with his first touch or his control, just that when he gets the ball in a tight spot, sometimes he'll get out of it by passing, running with pace or dribbling, but often times he wouldn't know what to do, hence why I say he is NOT comfortable on the ball. at least not as comfortable as Shaw.
Remember , he is only 23 now, he will get better with his consistency with passing/crossing and his composure on the ball, since he arrived he's been on upward trajectory and he is been the most consistent RB in the league in terms of overall performance.