we arrive in Hong Kong 6pm 14 September and leave 4pm 19 September

It depends. If you will use the Airport Express during the days and the MTR, the Travel Pass should be the choice. It includes the single or two journeys on the express train and unlimited rides on MTR for 72h. If you also wanna use other transportation like ferry and city bus, just top it up once you get a card. But you will only use the MTR, buses, ferries, the Standard Card can be accepted, with which you can get some discounts onboard.