are reproduced charts made to fit the scale of a chart table on a non commercial
boat. Other companies do this too and make regional folios. I find them quite adequate and use the one for our area all the time. You may also like the Admiralty Leisure Folios http://www.admiraltyleisure.co.uk/ALD_FOLIO_NM.asp
as well as they are in English
. As you note Sportbotkarten is the same thing but in German.
You comment "too many obsolete charts" I don't understand. Some charts don't get updated that much and all these companies just reproduce them. They don't make new charts so no one company has "better charts" just different ways to package them. Scales and coverages for the actual charts vary since the folios are made from the official charts and also rescaled to fit the folio format. The scales of the charts will never be all the same scale because the original charts are not of the same scale.
Folios are a way to get decent charts at a lower cost plus be able to store them aboard. The Bellingham folio for the Adriatic
is priced about 1/4 the price
of the charts purchased one at a time and are offered in a smaller or larger folio format.
If you are looking to purchase
charts I would seek them in what ever language you speak "navigation" in best. Notes on charts often mean very important things and you need to be able to read them and understand all notes.