I have the 1.4 and really like it. Not sure how much I would appreciate the extra speed of a 1.2. It would be a safer bet to start with the 1.4 and go to the 1.2 if you had to than to go the other way. Looking at Bryan's ISO12233 crops, the 1.4 looks comparable or better than the 1.2 across the entire aperture range. See here.