True up to a point, but if you arrive late night and leave early morning, it does not really make any sense to go into the city centre, especially if you need to return to the airport to pick up a car the next morning in any event. Moreover, the OP has an arrival time of "around midnight". The last tram from the airport to the city centre leaves at 00:35am. If the flight is delayed for any reason, it could be past the time of the last tram by the time they have collected their baggage and exited the airport. It seems to me that, unless there is an overwhelming reason to go into the city centre, an airport hotel makes more sense in this situation.