Originally Posted by
dj_jay_smith
I would suggest to skip the section between Mainz -> Rüdesheim/Bingen as it is not as interesting as the later stages. Instead, take the train to Bingen and take the boat from there either to Boppard or Koblenz (depending on how long you want to spend on the boat).
This. Bingen preferably because there are semi-fast trains to Bingen from Cologne. You're stuck on the "all stations" train if you want to go to Rudesheim.