Just to clarify
Firstly, I dont give a hoot what people shoot with, its the results that count.
Secondly, I am fairly anti the "prescriptive sorts of comment" where for example people say "you need full frame to shoot a wedding" quite frankly, you dont, and a couple of years ago, the facility wasn't really an option
Thirdly, Like most people who shoot for a living, I see my gear as a tool that needs to pay for itself, and in the next round of cameras I buy, I will do what I always do and buy what I need, which doesn't always mean "the best money can buy"
I do agree that if you want to sell huge prints & canvases having a camera that produces a bigger cleaner file is advantageous, I do wonder how many people are actually selling such prints in enough volumes to justify a camera choice
Nowadays the whole ISO question has been covered in both crop and full frame cameras
My tongue in cheek observation about 'blads is that apart form the ISO issue, they comprehensively cover off all of the other reasons why FF is "better" (and some)