I have owned all the 'A' and 'M' 50mm (from f1.4 to f2).
Still have all the 'A' versions and a M50/2 (though I like the build of the 'M' ones so much more).
No difference in sharpness in the center on any of them at the same f-stop.
Never bothered to compare edge sharpness.
Use a hood to cut out loss of contrast is important as well as accuracy of focus.