See the past Yeshurun that just came out (elul ????) a 100 page article on this topic. He concludes that the MB was the go to sefer in Europe when there was no Minhag. He theorizes that this is true because he did a much more thorough job. See there for many many sources.
To PAA again if you know of any sources about this methodology please write them (you realize that with such a claim you are taking on many accepted ??????? as stated previously, therefore it would be helpful to have a source) . In the article he also discuss Rav Henkin and the Teshuva you quoted previously Beny Bonim without quoting it by name just the author.