Irish Rambler, we liked Dortmund,especially the castle,and the river. We were recently in Frankfurt,saw many new arrivals, and felt very uncomfortable in some areas.
Hector, the standard is an inflatable. Light, easy to carry up a beach, easy to store, convenient, and buoyant. They do like an outboard though and best not bump into hard sharp things. Plastic, alloy, wood, will likely be more durable,but heavier. We`ve had our inflatable 11 years, I`ve done one lot of repairs,it`s still good. But beware of buying a used one unless you are sure about it.