My only comment is a woefully unscientific and unobjective one: I prefer the rendering of the 20mm to the 25mm in most of the comparisons except the one with the close focus points of the bird house. In that one, the 25 wins out by a hair. Also, weirdly, in the nighttime shots (of all the vans lined up), I like them both. But for me, the differences really come down to how the different FOV's affect what one can do with the lenses; for me, the 25mm almost feels a bit more of a telephoto, while the 20mm corresponds more to how I 'see the world' normally.
With regards to focusing speed, I've owned 3 copies of the 20mm; my first was the v1, my second the v2, and my 3rd is also the v2. With regards to the focusing speed (AF quickness) questions, once again my own (admittedly subjective) perceptions are on the weird side: I found the first generation (v1) copy of the lens to focus very quickly - while both of my copies of the v2 either focused more slowly (than the v1) or occasionally 'hunted' (which my v1 never did).
I think the lenses are different enough that one could relatively easily justify having both - possibly on different bodies. But my fondness for the 20mm means that whenever I have one, it usually 'lives' semi-permanently on one of my favorite mu4/3 bodies.
Thank you for a great - and quite thought-provoking - comparison of these lenses, David. It's given me (and keeps giving me) food for thought.