.
FA 50 1.7
plus: Sharpest, very sharp wide open, nice colors/contrast
minus: Bokeh can be busy, smaller FOV
DA 40 2.8 limited
plus: Very sharp, best edge-to-edge, bright colors, good contrast, no CA,
fast to lock focus, tiny
minus: only 2.8, hard to MF, not quite as sharp as 50 1.7 or 43 (but still
exceptional sharpness and sharper than any zoom.)
FA 43 1.8 limited
plus: Maybe as sharp as the 50 1.7 at f/2.4+, rendering is FA-limited, very 3-D because of center sharpness and specular highlights. Build quality is exceptional, will probably last forever, MF is nice.
minus: More expensive.
As you can see, all three are fun to own. Right now I only have the 43, sold the
40 and FA 50, but missed the FA so I found a cheaper F 50 1.7 that's just as good.