Ruben ... are you writing a book with all those academic questions?
For the majority of people (95%??) taking pictures nowadays (seems almost everybody)
There has not changed a thing .... they bring the cf card to the lab instead of the film ... that's all. The lab does somee "autotweeking" and voila!
The only processing they do is deleting the files they do not like on screen or selecting the best.
I think in general .. for the snapshooter (the giant majority).. they get far better results from digital than they ever had from film!
Perhaps partly because they use better digital cameras than the film cameras they used.
Partly perhaps because they shoot tons of pictures now and just 2 rolls a year in the filmdays.
If you want the question answered for the dedicated photographer things get far more complex ..... you have to start manipulating your own files .. for that you need a callibrated screen and you need a lab that does not autotweek your files. For a minimum that is.
For B&W tonality with digital i think i gained from using older lenses on the R-D1 (Pre-asph lenses ) .. an option not available on my Canon DSLR.
Of course procesing skills also play a role .. far beyond the capabilities of the camera ... (because they are all capable of excellent results in the right hands).
Just some random thoughts because i think there are no general answers to your questions
Han