Hema maps come in a variety of scales.
Off road maps are generally raster maps, which means that they are a "picture" of the map.
Street type maps (like thos found in iGo, Garmin, and Tom Tom type GPS devices), are "vector" maps, which means that they are generated on the fly as you view them. They are generated from data which determines the road geometry and features.
Depending on the availability of source data, and the intended use that the maps will be put to, scales may vary widely in off-road raster maps.
There is a fairly common perception in the market that the only maps which are any good are higher scales (ie. 1:25000, 1:50000).
Just because a map is 1:25000, it does not mean that it is somehow a "better" map. You need to evaluate what you are using the map for to determine a suitable scale.
Here is some explanation regarding differing map scales etc on the Hema website: