I have the FA 35 f2 and I am very satisfied. I cannot comment on the optical quality of DA 35mm f2.4. I collected that the FA was a good lens and I chose that because of having a metal mount and being FF. In case Pentax ever produce one.
If you are interested to get the FA, you better check BH. The lens new at BH costs 399 $:
|No Lifeguard on Duty by io_bg|
from Break the rules
|Inside A Clock Tower by poppyjk|
from Gear or Gears
|READY FOR A MISSION by DIM POL|
from Fighter aircraft