If you fly with land luggage only (as I do) and can check in and print boarding pass 2 weeks in advance (with AirAsia) then I think advantages are obvious. You can arrive at the terminal one 1h before departure and go straight to the gate.

Secondly, only 45 min from above mentioned 4h is spent on flight. The rest of the time you move around/use other means of transport. With bus you sit in the same seat for 5 hours.