Most companies still expect people to document their availability and absences. Some people still frown upon those that don't follow the butt-in-seat rules. So

Most companies still expect people to document their availability and absences. Some people still frown upon those that don't follow the butt-in-seat rules. Some managers (I've had some really bad ones) will try to keep you under your thumb if they can. Everything else equal, I would prefer to explicitly have the days off and not have to deal with that.