This winter, I sold my Panasonic 20 mm f/1.7 that I bought the summer of 2017. The reason I bought it was that I wanted a standard lens and had seen enthusiasm about this lens in some online reviews. It seemed like the perfect walk-around lens with its 40 mm full frame equivalent field of view, small and light pancake lens design and wide aperture. The focal length is a nice compromise between a 35 mm and 50 mm equivalent lens, and the image quality is good.
The first day I had the lens, I used it for some street photography and I missed some shots because of the slow autofocus. That annoyed me quite a bit. The slow autofocus continued to annoy me in the months to come whenever I used this lens. I really liked the image quality, the small and light size and the fast aperture of this lens, but even so, I did not use it much since I was unable to trust it to deliver the results I was after when needed.
Last spring, I found a cheap, used Panasonic Leica 25 mm f/1.4 Summilux. With that lens, I get the 50 mm equivalent full frame field of view and a slightly wider aperture than the 20 mm f/1.7. This lens has a beautiful colour rendering and is just as sharp as the 20 mm. Even if the lens is larger and heavier, I find myself using it a lot, whereas the 20 mm f/1.7 has spent most of its time lying idle in my bag. With the wider aperture, portraits and close up shots of objects with a nicely blurred background is easy to achieve. The longer focal length also contributes towards this. (Not that it is hard with the 20 mm either, but it is even easier on the 25 and the quality of the out of focus parts of the image is slightly nicer.)
The focusing speed is also much faster on the 25 mm than on the 20 mm. This means that I never miss a shot with this lens. That is actually more important to me than the size of the lens. The 25 is twice as long and with the lens hood maybe closer to three and a half times as long as the 20 mm, but it is still smaller and lighter than full frame 50 mm lenses. After a few months of using the Summilux as my standard lens and not using the 20 mm, I thought I would rather sell it and get some return on my investment instead of wasting money by having it lying on a shelf.
Sometimes, the 25 mm is a bit narrow in its field of view and the 20 would actually have been a better focal length. As a walk around lens, the 20 mm focal length is slightly more versatile so I do miss its focal length although I do not miss its slow autofocus. If Panasonic updated the 20 mm with faster autofocus, even if the updated version would be slightly longer and less pancakey, I would get it and probably use it a lot since I like the standard lens perspective, but find 25 to sometimes be just a little bit long.