Go for the FA31mm f1.8.
My first lens was the DA18-250mm. I love the lens versatibility, and its IQ is decent. But it cannot be compared with the FA31mm f1.8. I have both and the FA31mm is outstanding.
The FA31mm f1.8 is also surprisingly versataile for a prime. The focal length is wide and not to wide, with negligible lens distortion. The IQ is outstanding. (Truly.) The lens is also fast and can be used in low light almost as a fast prime.
As indicated by others, you cannot get wrong with the FA31mm f1.8. Go for it...