For post number one... I have seen DirectX 9.0C games that look as good if not better than some DirectX 11 games.
For post number two.. I have played games that utilise both DirectX 9 and Direct X 11 and in some cases Direct X 11 performance has dropped by half for little visual improvements.
As has been stated, it entirely depends on the experience of the graphics team. I would much rather play a well developed DirectX 9 based game than a poorly developed DirectX11 based game.