In my book, you hassle when you push up, you stand off when you drop deeper. Basically, hassling will mess up your positions, which can work further away from goal, and if all players subscribe to it (very fluid philosophy). When you are defending deep, you want to deny passess, and intercept the passess by being in correct position, not by running around (very rigid philosophy). Otherwise, opponent can exploit space, and since they are near to goal, get to easy goal scoring opportunity. When hassling, you have an option to defend using the offside trap and playing narrower and by using two defenders on defend, or by using two stopper duties and playing wider. Naturally, the narrow variant will be more effective at pressing, whilst you will have easier time scoring with wider approach, and it should be easier to pass through opposition if you play wider, too. When hassling you can use players with aggresion as primary attribute, and when standing off you shouldnt.