In the end, it's all about the image (and, even moreso, the photographer's ability to get the right image to the right publication in the right timeline). I did newspaper feature photography thorugh the 1990s, preferred rangefinders but carried SLRs about half the time, and it didn't really make a difference as to the quality of the image because of the other variables in photojournalism.
Newspapers always have been notorious for treating photojournalism as a commodity. Spend hours crafting, editing and fact-checking a written article, then spend about 11 seconds slapping on a wire image or grabbing one of the staff photog's shots. This isn't universal - there always are good photo editors out there and editors who appreciate photography. But for speed, convenience and cost, newspapers used Speed Graphics during the rangefinder era, went SLR in the 1960s and digital SLR by the early 2000s. I've seen books from the 1950s that draw a sharp distinction between photojournalism (telling a story with photographs) and newspaper photography (getting a single image that tells the story).
By and large the customer (editor of newspaper, magazine, wire photo desk, picture agency) doesn't care about the technology so much as the image itself. This is especially true in the post-darkroom era. SLRs have dominated the photo business since 1960s. But there always are photographers who win major awards or get major audiences using rangefinders and other non mainstream equipment. (There's an award winning combat photographer who uses consumer small-chip non-interchangeable-lens digitals; there also a few years back was a DC photojournalist who took magazine pictures of the president, congressional hearings and other news events using a Speed Graphic.
And a few passionate photographers always have won awards and business with rangefinders, film or digital. The kinds of photographers who are fully dedicated to both the craft and ethics of photojournalism are the ones who win awards and get recognition from their peers. Sometimes, but not always, these are the people who care enough about their mental and physical relationship with the camera itself that they gravitate to Leicas or some other specialty camera. On the other hand, these same people often care so much about the image process, about the human interaction that goes into getting such images, that the camera they're using is largely irrelevant. They would take masterful, memorable photographs with Speed Graphics, Canon G10s, Leicas, or their niece's $34.99 pink Barbie digicam.
