The 20mm f1.7 should really be reviewed and tested by DXO. I guess it won't because it's been an embarrasingly long time since its introduction. However, this really is the competition and to complete a more accurate review, one should show how the Pany 20mm f1.7 compares to the Olympus 17mm 1.8.
My guess is we can pretty much assume the Pany is a little better but we'll never get this analysis on this website. Pity.