From the Garmin website ("https://buy.garmin.com/shop/shop.do?pID=6299&pvID=7876#coverageTab") you can reach a preview of the
"City Navigator Europe NT 2009" map.

http://www8.garmin.com/cgi-bin/mapgen/webmap.cgi?p=24772609&l=0&u=1&v=0&cp=493DDBBB5FF2CE08&z=2&x=300&y=113&w=600&h=450&d=2&rz=0&k=1&sc=1

You can see that they have some different data compared with OSM: some old data (e.g. obsolete old train tracks which are removed for some years) and some false data (e.g. gas station at complete wrong places) and some things which are not yet mapped by OSM.