Couple of issues I have found with PickingType.SHADER.  If your app loses Context, when it gets recreated - if you use PickingType.SHADER, you will need to reset view.mousePicker = new ShaderPIcker(); otherwise your setup picking will not work.  This is not an issue with out Picking types.

Also on iOS if you try PickingType.SHADER, the entire scene will flicker to black when you interact with your finger.  Also because the screen goes black the mouse picking fails, meaning picking that would work on desktop does not fire any events.