Can’t speak for the 8-25 as I’ve never owned one, but the focal length is very tempting as a true walkable lens. I do however own the Panasonic Leica 8-18mm, and have done for around 8 years. Don’t know if it’s just my copy but it’s optically brilliant at all focal lengths, and having that F2.8 at the wide end has come in handy a few times. I also like the fact the the overall length of the lens doesn’t change when zooming. The Olympus 8-25 being a newer design, might be better optically, but to do that it would need to be pretty much flawless to beat the 8-18mm. The Panasonic lens is also around 100g (25%) lighter if that makes any difference to you ?