Pro: Historians from about 1880 to the Depression were concerned about the craft as a profession. They looked at it scientifically in the sense that they saw all historians working to add more and more certainty to the historical record, a little bit at a time. Not because they felt they would reach perfection, but that they were creating a better historical record all the time. They were developing the tools and methods, philosophy and expectations that we still use today, often time unaware of it's origins.
I find only pro and very poor choice of todays historians, Picard could discuss a topic as Bonaparte and Moreau in one book without the attitude of todays writers, today, you will find either pro Bonaparte, hail all glory or damnation, down with the ogre, books like those of Tulard or Presser - are already publihed a time ago as well.
Another Pro is that the authors of the last century tackled topics which are out of vogue and not mainstream of today, like a series about French Revolutionary Cavalry in three volumes.
Hans - Karl