40 mm or SWC is a continuing story. Many words have been used to describe pros and cons of these options.
Pro for 40 mm:
Easy control over composition, fits existing body, in case of CF version excellent IQ although the older C lenses are very good too.
Against: Higher distortion compared with SWC, heavier this goes certainly for C lenses. Large expensive filters B 104 for C lenses and 93 mm for CF/CFE
Pro for SWC:
Smaller and easy to carry, silent operation allows snapshots without being noticed, almost free of distortion.
Against:
Image control with viewer less acurate, better image control with rear fitted screen adapter possible.
More expensive than a decent 40 mm: C lenses from 500 euro, CF from 1300 euro. A clean SWC even older early ones will set you back 1500 euro.
SWA camera, predecessor of the SWC introduced 54 years ago at the Photokina by Victor Hasselblad
500 CM with 80 mm CF and 500 CM with early 40 mm C lens.
With a little luck an early 40 mm C lens with excellent glass can be found under 400 euro.....
Wilko, show us some of those excellent images, for instance the Berlin ones taken with 40 mm CF lens.