As others have said above it would depend on the type of picture you want to use it for.
Landscapes, I would go for the 28mm simply for the extra 2mm. I have a copy of the Minolta version, its a tad soft at f/2.8 but at f/3.5 its spot on. As stated above and by many others the lens is noted for a number of issues, I am yet to experience them and going by Dyxum reviews I think it depends on the lens.
Portraits, Shooting portraits with wide lenses can produce odd deformities and off perspectives. Idealy you want to be somewhere between 50 and 200mm for a good portrait lens. If your intending to buy the lens for portraits, I would also look at the Minolta 50 f/1.7 and the Sony 50 f/1.8.