You could do this either way, depending on what you want to drop down.

If you indend to drop down a menu, like a context menu or a popup menu, then the Buton panel style is probably easier. You just handle the button click event and show the menu. If you need something more complex, like a dropdown list or a ComboBox or you want to drop down a control, then you would have to use a ControlContainer and place a control inside the panel that does what you want.