Airport distance can be misleading
Some airport hotels are walkable from a terminal, while others require a shuttle, train or taxi. Include that transfer in the real cost of the stay.
Check shuttle hours
A free shuttle is only useful when it operates for your arrival or departure time. Early flights and late arrivals are the times to verify schedules carefully.
Compare the airport rail line
In some cities, a hotel one or two rail stops from the terminal can cost less while remaining almost as convenient as an on-airport property.