Moselle river cruise from Cochem

I can't say I've done either one, but you can easily see the scenery from Cochem to Treis-Karden by riding the local train on that route that follows the river. It is only 7 to 10 minutes each way, and you can do the round trip in under an hour. There is no rail line between Cochem and Beilstein, so I guess I would opt for that one.

I have done the Cochem to Beilstein cruise. It goes through the locks, which are interesting.

I actually prefer renting a bicycle and pedaling my way toward Beilstein, then crossing the Mosel on the little ferry with my bike.

I second what Joy had to say... we rented a bike in Cochem and cycled to Beilstein (there are some great lunch options there), and then took the boat back to Cochem. Best of both worlds.