I've owned all those listed, my pick for every circumstance (except 2) is the FA43.
the two exceptions are:
1) quick shooting in the street, as the da40 focuses a bit faster than the fa43 and has quick-shift focus feature, and the exposure is a bit more consistent from f-stop to f-stop (the same +/- exposure compensation yields the same results at different f-stops, whereas the fa43 can be a bit more fussy, worth it, though, except in quick street type stuff)
2) if you need more even sharpness between center and edges (as others have stated) I usually don't, so works out nicely for me, and when I do need it, like landscape sceneries, etc.. I am stopped down enough, that it is no longer an issue.
this is at f1.9 wide open, I messed up the focus, and at 1.9 not much room for error.... or maybe its wings were moving too fast for the shutter speed.