Regionwide vs Region maps

There is no difference, except that region maps are based on administrative divisions

Source

Geographic Regions

Data on the download server is organised by region. The /openstreetmap directory contains files that have a whole continent's data in them, and for some continents there are subdirectories in which you find individual files for various countries. Some countries again have their own subdirectories with data for administrative subdivisions. For Germany, all "Bundesländer" are available as separate files, and for England we have many individual counties.