I've heard that unsalted butter makes it easier to measure the salt to put in a recipe, since you don't need to reverse engineer the salt content of the butter.

I've heard that unsalted butter makes it easier to measure the salt to put in a recipe, since you don't need to reverse engineer the salt content of the butter. But in practice I don't find this very compelling because (in my experience) the salt is pretty standardized. I generally convert my own recipes back to using purely salted butter so I don't have to stock two kinds of butter.