I have/had both lenses and systems. I replaced the 20mm nikon with the 14-24. to me it seems like the decision should be based on what and how you shoot. get the nikon if you mainly do handheld, the pentax if you shoot off a tripod most of the time. I do sometimes handhold my P67, but it primarily sits on a tripod for its use. mirror lockup is a must in my mind for the P67 with any shutter speed slower than 1//125.
I found that for me in the 35mm cameras, that 20mm is to wide for most uses that I use them for, 28mm being my most used wide angle lens. with the P67, I use the 45mm more, but prefer the results from the 55mm. the 45mm is a good lens that can be had for not much money. comparing a mamiya 6/7 to a P67 is apples to oranges. I use my mamiya only handheld, the pentax tripod only.
for the price they are being offered at today, I would get the Pentax 45mm.
john
I found that for me in the 35mm cameras, that 20mm is to wide for most uses that I use them for, 28mm being my most used wide angle lens. with the P67, I use the 45mm more, but prefer the results from the 55mm. the 45mm is a good lens that can be had for not much money. comparing a mamiya 6/7 to a P67 is apples to oranges. I use my mamiya only handheld, the pentax tripod only.
for the price they are being offered at today, I would get the Pentax 45mm.
john