Although I agree that most lenses are best between F8-F11, I do not agree with ignoring the F-stop. The best lenses are made to be used wide open. For Canon L lenses are designed to be very sharp wide open - unlike the kit lenses which tend to be extremely soft. I use most of my lenses wide open a high percentage of the time.
If you take Sears portrait style shots, then yes the f-stop of the lens won't be as important because you will not be shooting wide open very often. However for more artistic style shots I find the nice bokeh from a wide open shot far more appealing.
The other thing is I have noticed that you do get what you pay for with most lenses - as long as you truly need it. If you are just posting on Facebook and FlickR you really don't need that ultra sharp lens with minimal distortion and color fringing.
I gather from the original poster that he actually intends to USE his 50mm lens. He is just trying to figure out which one is the best for his needs. In terms of that matter I would put the 50mm lenses into two categories.
Macro 50's - Canon 2.5 and Zeiss 2. The Zeiss is basically superior in every category, but unfortunately also in price.
Portrait 50's - Canon's 1.8, 1.4, and 1.2. You can probably also add Sigma's 1.4. In terms of which works best that depends on your needs. If you're on a super budget get the 1.8. I know several people who's 1.8's have fallen apart though, so if you have the money the 1.4 is the much better choice. Yes, if you take care of the 1.8 that can be less of an issue but the fact is if this lens is being regularly used it will get banged up.
I have heard that the Sigma is better than the Canon 1.4, but I have a hard time trusting the quality of Sigma. For the record Zeiss also makes a 1.4 for Canon.
In terms of the 1.2, if you have the budget for it rent it and try it out. From using this lens for the weekend you'll have a very good idea whether this is a lens you'll love or hate.