I have experience with the exact same lenses, except only using them on digital. And, technically, it was the 'optically identical' siblings: A50/1.7, M50/1.4, and F50/1.4.
I did notice the M50/1.4 had a strange glow. I got it for a good price along with a couple of old K2s, a K50/1.2, and some worthless junk. It was fairly easy to decide to keep the K50/1.2 and make myself sell the M50/1.4. I already had the A50/1.7 anyway.
While the FA43 will be slightly wider, I don't think it's too much. It's clearly better than any of the aforementioned lenses except the K50/1.2 at any given aperture. It's even noticeably better than the F50/1.4 (which is already slightly better than the FA50/1.4, from what I've seen).
The FA43 doesn't have amazingly smooth backgrounds - it seems rather average in that regard. In fact the backgrounds are almost nondescript, it seems. But the foreground subject and the colors are wonderful - probably the best colors you'll ever see on whatever color film you use. And my early serial MIJ FA43 is probably even slightly better in this regard (the colors) due to what must be slightly different glass. But my AIV FA77 was certainly no slouch - on that lens I never felt shortchanged by not having an MIJ version.
---------- Post added 02-27-14 at 08:48 PM ----------
Originally posted by Nuff I'm thinking of also getting a 50mm f1.4 or f1.2, but only for the extra speed and not field of view.
It's either the f/1.2, the DA*55/1.4 (if it'll work on your camera), or don't bother.
If you go with the f/1.2 make a deliberate choice between the smc "K" and A versions. I like the backgrounds on the K slightly better. But
technically speaking, the cause of that should probably be called an optical flaw. So decide which you like better, and how much the A contacts matter to you.