Quotes from this thread -
http://www.photo.net/equipment/canon/ef50/
"Canon's 50mm f/1.4 is sharper, has better bokeh and construction than their f/1.8, whereas for Nikon the f/1.4 is better built and has better bokeh but is less sharp than the f/1.8. This simplifies the decision-making process, as there is only price vs. quality to consider, not multiple trade-offs"
"I retract any positive suggestion about the quality of the Nikon 1.4. I sold that lens and went with their very fine 1.8D lens"