Hi Rick,
I've never tried the 2.8 but for reasons I won't bore you with I currently have two German-made 1.4 AEs in my possession. Optically there is very little to choose between the two ex&les, both of which are fairly well-used (I picked up the more expensive of the two for 300 GBP).
Both of them are extremely sharp beyond f/4, and give very good bokeh. However, I was shocked by the performance up to f/2, as both lenses are soft to say the least. A Canon 85/1.8 EF is appreciably sharper at f/2, for ex&le. I can post cropped test shots at f/8 and f/1.4 if you want to see what I'm on about, but all this is in accordance with the MTF results on photodo.com (which I didn't make the effort to fully understand before setting out to buy).
However, I've got no regrets about the 1.4 because if you stop it down a little it is definitely one of the world's sharpest lenses. Even at wide apertures it is still valuable, because the soft-focus effect it produces can be used to good effect, but don't expect sharpness at those apertures or you'll be disappointed.
HTH
-= mike =-