When I bought the aspherical 35 1.4, I sold my pre Asph 35 1.4, and I still regret it.
Although it is less good wide open than the Aspherical one, it is much more compact and very good at medium apertures (from f2.8). I would have used it as a compact lens on my M6, allowing 1.4 if really needed. The aspherical and asph 35 1.4 are at least twice as big as the previous one.
To me the pre asph summilux 35 is a bit soft at 1.4 and prone to flare, but at the medium apertures, it becomes very sharp, and due to its slight field curvature, it produces pictures which are very sharp at infinity, but also in the corners, at closer distance.
I should have kept the pre-Asph and got the aspherical one in addition, but the money did not allow it.