I learned from a discussion on another thread that the canon 50 f/1.2 has really nice bokeh due to that being a primary factor in its design. Apparently some spherical aberration was designed in for that. The canon probably has more consistant af? I would like to see some real world samples comparing the canon and sigma because for me the choice would be between those two lenses and not the otus, even if they all cost the same.
I too would like to see a comparison of those two lenses -- for overall rendering of various subjects. The Canon 50/1.2L has been my main 50 for a long time and I love the way it draws. It is simply beautiful. The new Sigma is interesting and no doubt sharper wide open, but will it draw as beautifully? I'm not sure I'd want to carry the bigger & heavier Sigma for the extra sharpness alone.
As for autofocus, the 50/1.2L really benefits from the improved AF of Canon's top-end cameras (currently the 1DX or 5DIII). It is a better autofocusing lens with the 5DIII than it was with the 5DII. And it is a better autofocusing lens with the 5DIII than with the 6D.
The Otus is will likely prove to be the best 50 for a DSLR. But due to size, weight, price and manual focus, the Otus will not be a practical alternative for most photographers.