An f/1.4 lens is a stop slower than an f/1 lens (of the same focal length).
From what I've heard, the 50/1.4 is good. However, I've never owned one and don't have the 50mm focal length in either prime or zoom (I don't like it).
This review might be helpful to you:
http://www.the-digital-picture.com/R...ns-Review.aspx