I had the FA*24/2, but it was not sharp enough for me on the edges on the A7 (though the A7 does have a thick sensor stack that may actually have made it worse than it should be).
The M20/4 is really nice because its small and portable.
Its only poorer in sharpness on the last 1/10 or 1/8 of the frame.
Put in the lens corrections or a 5x7 crop for composition, and most of that is gone anyway.
In the context of cityscapes, I find that 24mm is really too narrow since its hard to step back for framing and vantage point limitations.
20mm is barely enough actually and often, with the 20mm, I need to shoot in the portrait orientation.
So for citiyscapes, as wide as one can get is usually necessary.
Samyang 14mm
Voigtlander 12mm (not a PK mount lens)