At short distances (1 m or so) and in the center, the 50/1.4 AIS is slightly sharper and has less haze than other Nikkors, according to a test I ran with my different copies (50/1.2 AIS, 50/1.2 AI, 50/1.8 AIS, 50/1.8G...) set at the same (wide, 1.4-2.8 ) apertures. Otherwise, the G is more uniform and has less coma.
The only trouble for me is, wide open performance of the 50/1.4 AIS is still somewhat feeble (too much purple fringing), at least for color shooting.
In the meantime, my preference went to 50/2 lenses with a clean f/2.0 (Zeiss, Leitz Summicron R).