What is the main difference between the ajaxStop and ajaxComplete global handlers?
There is no difference. They are aliases of each other.
ajaxComplete fires when all open requests have completed, while ajaxStop fires when an individual request completes.
ajaxStop fires when all open requests have completed, while ajaxComplete fires when an individual request completes.
ajaxStop fires when an error has been encountered, while ajaxComplete fires when a successful request completes.