oooooh. 1.4 if it's a choice, but you've got to be precise with your focusing50mm 1.7 or 1.4?
I had a 1.7 that came with my Pentax ME Super that I bought when I was 15 for my birthday. Really wonderful lens. Then a few years ago gave it to my youngest. Bought a replacement (ridiculously cheap, about £13 ebay iirc) which was good but then gave that to my eldest. Now I'm waiting for a 1.4 from eBay. I think the 1.7 has better reviews and the 1.4 by most accounts is softer, but I just love the bokeh!