On the question of scale, it's hard to say. I take your point that if things go wrong and you're small, the consequences are not as dramatic, but there can be real advantages of scale, of being bigger. There are economies of scale once you know what you are doing.
To your more general question about where the answer lies, I don't have that answer. We're always having to weigh off different values. Ultimately, it has to be a financially viable project for whoever owns it. No one is going to grow salmon as a charity. Beyond that, if the choice is between trading off local effects from global, someone has to take that decision, and there is no simple equation to work that out. It is about the values that you all bring to the table.