I have the Canon 50/1.4, owned 5 Canon 50/1.8's. Reason for selling the 50/1.8's- Too Good to get so little use. I tend to favor Sonnar formula lenses. The Canon 50/1.4 is one of the few 6 element F1.4 lenses made. Canon had a new glass and made good use of it.
The Nikkors are higher contrast, probably due to them being Sonnar formula lenses with less surfaces. The Nikkor 5cm F1.4 is more harsh for out-of-focus areas. The F2 lens is much smoother. The Nikkors give higher center resolution, at least mine vs the Canons that i have shot with. The Canons are better corrected for flatness of field.
Here is an old test with the Canon 50/1.4, Nikkor 5cm F1.4(early), and really good J-3.