[GEli]

Well, for the price I would call the 50 f/1.7 a better value. They can be had for around $40 as opposed to the ~$200 most 50 f/1.4s are. Of course you also lose AF, which is a rather handy thing to have, so depending on your budget and your fondness of manually focusing either will work. They're both very similarly sharp (tack sharp with ever so slight softness when wide open). I settled on the FA f/1.4 because the used market for Pentax glass in my town is terrible and shipping in old lenses tended to remove any cost benefit to buying old glass. (Asking this question on a Pentax specific forum is one of the few ways guaranteed to start a fight that's sure to end in at least 3 bannings ).

As for 35mm, I've only played with the newer lenses at local camera stores so I can't really comment on older versions. The FA 31mm f/1.8 Limited is gorgeous but huge and expensive, while the more affordable FA 35mm f/2 is not as well made (plastic and such) but still produces very nice images.