I never played 1.0 but if you were to compare DX9 vs DX11.. it's obvious DX11 would have better graphic, tessellation makes graphic enormously better... unless your graphic card doesn't support DX11 then you wouldn't be able to see it anyways.

.. Then again, I dont know if 1.0 had tessellation, but it looks like the 2.0 has SAO in DX9 so it would be weird to be using DX11 without its key feature of tessellation in the first place.

I can't wait to get DX11 update soon enough.