On StaffTraveler, the number of actual open seats is shown. myIDTravel gets the loads from Amadeus, which provides the number of sellable seats. As airlines often overbook their aircraft, the seat availability shown in myIDTravel might be higher than the actual number of open seats. 
 
Also, the number of sellable seats provided by the airline might be capped. There may be many open seats, but the airline might cap this number to 9, for example. In this case, the number of open seats as shown on StaffTraveler might be higher compared to myIDTravel.
 
There are some more downsides of checking the loads on myIDTravel:
  • Very few airlines share flight load information with myIDTravel
  • The smileys are notoriously unreliable
  • The numbers don't show by how many a flight is overbooked
  • Numbers are unreliable and often outdated
  • Numbers are hard to find, read and compare

 

StaffTraveler shows the most accurate and up-to-date figures.