I have Airport CEO as well, but I find SimAirport to be more fun.
With Airport CEO, you are more of a manager, with SimAirport you are an airport and terminal builder, with a lot fun factor. involved.
Especially, setting up your terminal, which can be span 5 levels, from ground, 2 up and 2 down, for various things like baggage handling conveyor belts, sorting hubs, baggage claim carousels...
Additionally, SimAirport has a thriving modding community.