If your goal is to create a rounded border, you must use clippers only in the last situation, when containers may not help. For example, images can draw over rounded borders, so you have no other option unless clipping the image.
how about shape, shape vs cliprrect
RaisedButton( onPressed: () {}, child: Text('Test'), shape: RoundedRectangleBorder( side: BorderSide.none, borderRadius: BorderRadius.all(Radius.circular(50)) ),)