Thank you for writing.
By design, when you press on item the SelectedItemChanged and SelectedIndexChanged events are firing. When you click on the arrow only the SelectedIndexChanged event is fired which is an issue. I have added this case to our Public Issue Tracking System, so our users can vote for it. You can track its status and vote for it here: http://www.telerik.com/support/pits.aspx#/public/winforms/14042
I have updated your Telerik Points for bringing this case to our attention.
Let us know if you have any other questions
the Telerik team