Out of curiosity I had a short look at various map formats how much space they need for a certain country. I picked (for no certain reason) Bulgaria.
- 30 MB Garmin (openmtbmap, with contourlines (5MB))
- 41 MB mapsforge
- 57 MB Geofabrik osm.pbf extract
- 67 MB osmand
- 73 MB maps.me (streetmap (42MB)+routing (31MB))
- 98 MB openandro (with srtm)
- 100 MB Geofabrik osm.bz2 extract
PS: Of course various maps may contain a various degree of details in the data which I did not check.
PPS: Fixed OSMAnd and mapsforge after Zverik's hint (used a third party website before with obviously outdated data).