Again, lens choice is guided by the intended application of the individual photographer.
The lenses you mentioned are all very capable. There are always strengths and weakness with each one of the lenses.
If you are a prime person regardless of the photography style you adopt, Fa 77 and 43 would be amazing choices regardless.
Fa 77mm ltd gallery Fa 43mm ltd gallery
On the other hand, Da* 16-50mm is a lens I have given away to an old friend. Capable lens with stunning colour and contrast but lacking the necessary clinical sharpness. However, the sharpening could be applied with various style of sharpening techniques.
A capable zoom with the weatherproof capability for sure.
Pentax Da* 16-50 f2.8 gallery
If you do a search for Fa 77 and Fa 43, you would see plenty of discussion for pros and cons regarding these two most of talked about lenses.