The FA* is less sharp than the A*, which is probably deliberate- the FA* is an excellent, dedicated portrait lens, where maximum sharpness can be unflattering. I have the A*, and it is my sharpest lens- I can get more detail by cropping an image from the A*85 than from uncropped images from several of my longer lenses.
Check out this review where the A*85 out resolves the famous Canon 85mm 1.2 L:
Canon 85mm f1.2 L v Pentax SMC 85mm f1.4
Of course these are both film era lenses, but in this day and age when flattering softness can be added as desired in post processing, it may be preferable to have the sharpest available lens even for portraiture, which may explain the premium often paid for the A* lens.
Sparkston