I told RioRico that since I happened to have both of these lenses at the moment I would put some sort of comparison together. So, reusing some of my initial impressions, here we go:
Without the lens hood on the D-FA the overall size and weight is very close. The hood makes the D-FA twice the length and quite a bit wider than the A at infinity focus, and because the front element is so deeply recessed the A doesn't need a separate hood. Up to 1:2 magnification (where the A tops out) the sizes without hoods remain roughly the same, then the D-FA extends its length another 30% or so to hit 1:1 with the front lens element even with the front of its hood.
The focus ring is much lighter and smoother on my copy of the A (almost too light), however it has obviously been apart at some point in the past. I didn't notice until I set the lenses beside each other but the focusing scale on the A rotates past the infinity marking by about 1 cm in order to actually reach infinity (which I will fix shortly). Manual focus on either lens is perfectly acceptable for macro or portrait distances.
My initial impression is that both lenses are brutally sharp, meter well and produce colours that I'm happy with. The lens formulas are quite different, and the A has 6 aperture blades vs. 8 on the D-FA. The build quality of both lenses is excellent - much better than kit lens level, more solid and with better focus feel than an FA 50mm f/1.4 or other similar FA series lens, but a long ways off from an all metal Takumar prime.
Various photos to show size with and without the D FA's hood (keep in mind that the A 50mm only reaches 1:2 macro on its own at full extension):
And finally some comparison shots under a florescent desk lamp at ISO 800 and ranging from f/2.8 to f/8. I metered at f/2.8 with the D-FA and then shifted the settings in full stops until I hit f/8 with each lens. Hand held because that's how I actually use the lenses most of the time, and the little spider tank (Tachikoma) is about 2 1/4 inches wide by 2 inches tall at the highest point.
A at f/2.8
D FA at f/2.8
A at f/4
D FA at f/4
A at f/5.6
D FA at f/5.6
A at f/8
D FA at f/8