| As has been said over and over, one key is focal length preference. For me, in my film days I loved my FA50/1.4 (first lens I ever bought new) for general as well as low-light use, and a K135/2.5 for portraits.
Now in digital, for me the 50/1.4, I do use 50 FL but not for applications where I appreciate its wide-open softness and often I'm not looking for super-shallow DoF, so it's strengths in portraiture are a bit wasted on me in digital. I tried forcing myself to leave it on the camera, but it didn't stick.
On the other hand, threatened with rarity and a massive Canadian price jump, I just got the FA35, though, and its width + sharpness wide open I find great for indoor dim lighting, outdoor night shots, and general use. For me, it can be the live-on-the-cam general use prime the FA50/1.4 was in film. And the loss of one stop is compensated by the fact I can hand hold it at slower speeds.
....but that's just me. | 
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