FA also adds program shooting mode. It needs an AIS lens to work properly & shifts into a high speed program when anything longer that a 135mm lens is put on it (IIRC?). I bought an FA new back in 1986 & have been very happy with it. I have had no problems with it beyond the foam needing to be replaced.
I have an FE2 as well, picking one up cheap off of ebay a few years back. Out of the two I much prefer to use the FA. Two things that swing it for me are having an MD15 attached to the FA so find that it handles better & I prefer the LCD to a needle in the viewfinder. I also much prefer the FM2's LED viewfinder to the FE2's needle.
This is incorrect. Program works just fine with any ai lens so long as you have selected the minimum aperture on the lens. It will show a FEE error when moved from the minimum in Program mode.