.....Leica shooters make the wide open shooting rendition as an advantage, now I ask, how often users shoot wide open?
I can`t really understand why someone wanting top quality would spend serious money on 35mm, for the outrageous sum of a Leica, I buy a bigger negative 6x7 size M7II.
Still an RF, top quality optics, bigger negative, portable, etc etc etc!
So, whats the big deal about Leica?
Cheers
'
André
Your post in many respects answers the question of 'why is there no clear answer?". The closest you can find is a Mamiya 7 which is a totally different type of camera compared to a Leica M! Compare Leica Ms to Voigtlanders or Z1s by all means but you suggest anyone who wants 'top quality' has to ditch 35mm!!!! Of course the Mamiya 7 wins hands down on image quality alone, as does my Bronica RF645 (I know some Leicaphiles would debate this but I think they must be insane). If I had one camera in the world for everything, for me I would also pick the mamiya. If I was doing landscape work I would pick the Mamiya 7 any day. BUT if I needed a 35mm rangefinder (inconspicuos, small, lightish, fast lenses etc) and could afford it I would pick a Leica M...because a 35mm RF has many advantages over a bigger, slower camera! Technical quality is poorer with the 35mm, but the speed and small size allows for opportunities bigger cameras do not.
If you understand street shooting you would know that a lot of the best of that genre would never have happened had the Henri CB's of this world been toting about Mamiya 7s....
The 'whats special about Leicas' is two seperate questions as I tried to suggest before:
Why Leica M (because until recently it had no competition and in some specific respects still doesn't)?
Why Leica R (Because there are so many other SLR options)?
The answers are always going to be personal and some may run common to both (quality etc), but most people think Leica M when they think Leica.
Andre, in response to your posting, I think you miss the point: It would seem top quality to you would mean fine grain and the utmost detail. This is not the same for everyone and it is not always possible without tripod. For some top quality means 'being able or inclined' to get the shot in the first place. If you miss the shot on a bigger camera/format, youve got nothing, obviously. A grainer 35mm is obviously 'better quality' as it exists....

. Tripods not exactly being practical for street/documentary photography..see the below scenarios, all of which are from experience.
Just some thoughts on RFs (as you suggest a Mamiya 7 for 'better quality' [results]). I can fit my Leica M (or any small 35mmRF) under my coat and a 4 lens kit in my pockets or in tiny belt pouches. I can walk about all day unencumbered. I can even carry a spare body (at just over an inch think) under my coat on a strap without noticing. Can you do this with a mamiya 7? - No. You need a camera bag over your shoulder or you have to leave lenses at home. How do you think this freedom from bags affects my mobility, freshness, enjoyment of a solid day (or days) on the street? The Mamiya 7 is most definetely not an under the coat camera, but an over the coat camera - do you ever get concerned walking about with it in full view for hour upon hour upon hour, sometimes in the same area (or do you put it in your case and miss opportunities?). The use of a second body means even more bulk for you - an even bigger bag. For me, another 500g under the coat on a strap - its no bother. I can put 50/100 speed in one and 800-1600 in another. Along with fast lenses, who will be more flexible in varying light (yes you can put fast film in the mamiya 7, but your lenses are slower so you still are, well, much slower). I also now have that slow film body to close the gap on your 800 iso now even in comparative terms....You are now really screwed if you come out into the light as you have 800 film loaded and only a 1/500 top speed! Mine might be only 1000 (or 2000 if bessa) but I have a slow film body so can still shoot opened up. To be as flexible you really need that second body but get tired from the weight and walking...I stay out longer and take more shots....Where we can both shoot at 1/125 @ f8/11 your shots look better. But you have to mess about with shutter curtains to change lenses which you have to get from your zipped and strapped bag. I dont. You have to change film nerly 4x more often than I do, so I dont run out nearly as often mid flow' as you do. My camera focuses much closer for people shots and is less intrusive as it is half the size. I have no problem focusing my 90mm. Your 150 gives you tonnes of grief. Your rangefinder may (in case of quite a few Mamiya 7s) keeps losing alignment. Mine does not.
PS. If you choose aperture to get a specific DOF effect you need to stop down one to two stops more for the same DOF effect in any case. You therefore NEED a faster film to maintain a shake free shutter speed. You still have better quality overall even with faster film as you have whopper negs, but when you run out of F stops you are in real trouble. I keep shooting. Think this never happens? Ever tried taking handheld shots indoors, in train stations....cafes?
The Mamiya 7 is incredible, as is the RF645 (which I own). A competitor for a 35mm RF (Leica M) they are not, in many areas. They are far better in other way, but horses for courses. The only competition for a Leica M is another 35mm RF (or for R series, an SLR)! Then ask why Leica.........