Originally posted by Wheatridger
Ultimately I'll be the decider, but I welcome your opinions. I own both these lenses, and I'm starting to test them more thoroughly. But being in hock for my new K-3 lll, I'm strongly considering selling the 31 help pay it off. The 31 Limited is certainly special, even to this "magic lens" skeptic. But the 20-30 seems quite usable in the 25-35mm range on my K-1. It seems to have the same great bokeh, with much less CA and better coatings than the older 31 Limited, plus WR. The 31 is a little smaller, but a little heavier. It won't be much use on my K-3lll, because I have the F series and Takumar 50mm macros near that cropped focal length.
Has anybody else come to this fork in the road? Did you take it?
A zoom lens will always be more versatile in usability compared to a prime lens within the same range. The DA 20-40mm Ltd is certainly a quality lens, and features WR construction as well. I love it on my KP. That said, it becomes a matter of how often do you need the capabilities offered by the FA 31mm Ltd not shared by the 20-40mm Ltd such as the faster f/1.8 aperture? Everyone's needs are different.
As for myself, I found I'm not as interested in the angle of view from 31mm on an APS-C body, though it serves well enough as a normal lens, compared to having it on a 35mm body or a FF DSLR as a wide angle lens. If needing a fast wide angle on APS-C, the pickings are very slim to say the least, compared to a FF outfit. Only upon finally adding my K-1 II did I once again find more interest in the FA 31mm Ltd, FA 35mm f/2, and FA 43mm f/1.9 Ltd as a wide-normal. You'd need a 28mm f/1.9 to equal that one on APS-C, and if there was one it most surely would not be a pancake. This was one of my reasons for passing on the K-3 III (I'm happy with my KP), and going for adding the K-1 II.