So, I took the Leica 15mm with me the trip to Perth, because I wanted to see if my feelings on the lens are a little in my head or actually a creative consideration.
There is that snappy sharp/soft dynamic. The Oly usually lacks the snappiness of this lens, adding in a more natural, less obvious transition. It is no less sharp, just less showy about it. This technique was a common trick used to increase the illusuion of sharpness in the film era, basically increasing the perception of sharpness with contrasting softness.
The woman is sharp, her husband softer, son quite out of depth of field and the vendor a soft blob in the foreground. This is not how the Oly 17 would render this scene. Neither is better and in a perfect world a little switch on the side of one lens allowing either option would be cool.
Not a keeper on any other level, this file is ideal to show the sharp/soft/softer/softest character of the lens wide open. I would guess that the Olympus 17mm in the same space would have a gentler roll-off, making it more of a sharp, softer-sharp, soft spread.
Wide open sharpness is exceptional, snappy and crisp.