Thanks for all your suggestions. It looks like my friend will stay with DBPowerAmp CD Ripper on Windows.
Main reasons for him to stay with DBPowerAmp CD Ripper:
- it supports the Discogs metadata service instead of gnudb.gnudb.org
- easy tagging (single file, bulk file) is included
- cover art is downloaded as well
- ripped songs get a checksum and are compared with a remote database to verify accuracy. They call this “Accurate Rip”