The DropDownList widget creates list of object besed on the select's option elements. DropDownList also creates option elements of the select element in order to handle all possible scenarios of data binding. I will suggest you create a DropDownList from input element and pass the data as JSON. This will be the fast databinding. If you are OK with slower initial load, then you can set the autoBind:true. Thus the widgets will render there items initially. Please note that the SELECT element is a native control and it is hard for any widget to perform like it.
I attached a simple test project, which shows different possible implementations of DropDwonList.