I was not referring to rangefinders. A rangefinder will obviously be lighter, but as you mentioned yourself - is severely limited in selection of lenses, use of filters, close focusing, availability of acccessories (interchangeable finders, backs, power winders) etc. To me a rangefinder is always a compromise when various constraints dictate giving up some creature comforts.
As for DOF - at any given angle of view, a shorter focal length will always give you smaller circles of confusion at a given aperture. Whether you agree or not - it's hard to argue against physics. I have shot 6x7 almost exclusively for over 2 years and a variety of other formats for over 14 years. When critical DOF is at stake - a fixed focus plane 6x7 with lenses that only stop down to f/22 is not the ideal tool.