Hi Jason,
There are two main differences between populating a ComboBox dropdown and an AutoComplete dropdown.
1) The ComboBox dropdown usually only has to be populated once. Any changes after that can be a single addition to list. AutoComplete has to repopulate every time since the list of matches changes frequently.
2) The ComboBox can be populated ahead of time. AutoComplete cannot, since the list of matches is constantly changing.
However, I do agree that the dropdown becomes too slow once the matches breaks 15,000. I have entered
Feature Request #204 to improve the performance. However, I cannot provide any turnaround time on this request, or even guarantee that it is possible.
Regards,
Gregory Austin
Syncfusion Inc.