Why folding camera?
I don't know much about optical science, but from years of taking pictures
with many cameras, I can tell the differents between good lens and bad
Firstly, I impress with the classic look of them. Secondly, I was amazed by the design of machanics and size while folded. Lastly the optics quality of these older lens, mostly it has around 10 blades of diaphragm which produce smooth completed circle to out of focus spots (circle of confusion). The color saturation, sharpness, contrast and toning of the pictures maybe different from lens produced in these days, but the unique characteristics of the older days lens give different feeling, even use with modern films.
Both were made in German and had produced many kinds of cameras and accessories :