I totally disagree. DX11 is much better than DX9, and it is make possible kind of software emulation on hardware. very many things like texture conversion or TA-emulation in DX11 can be done on GPU using shaders, in DX9 it is not possible and uses CPU instead.
2D-games like "Metal Slug 6" is good example - on first boss I have ~7fps in DX9 and solid 60fps in DX11