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Here's your problem. If you want an image quality standard for f/1.4, you won't find it at 50mm, at least not from Canon or Nikon. Not sure about alternatives on the Nikon side, but the Canon 35L f/1.4 is better than any Canon or Nikon 50mm. The Zeiss 35mm f/1.4 is notably better than the Canon 35L, but manual focus. The Zeiss 50 mm f/2.0 is probably the best 50mm lens available from any manufacturer, but manual focus, and not f/1.4. I don't know much about the Zeiss 50mm f/1.4, except that it does not equal the image quality of the f/2.0.
I don't understand why there isn't a great 50mm f/1.4 autofocus lens out there, but there doesn't seem to be. Based on my own experiences with Sigma, I don't trust the Sigma fans to know what they are talking about. But they are praising lenses I haven't used, so maybe I'm the one who doesn't know.
By the way, even in the best lenses, edge sharpness and f/1.4 are incompatible, except in terms of the relative performance of various lenses, none of which will deliver truly sharp edges at that aperture.