I would actual lean more toward the ones that go from port-to-port in different parts of the world, not the floating casino kind (I rarely gamble, I just generally don't like doing it).

I normally like to spend at least a couple of weeks in a foreign country/region (depending on size) if I go, so I wouldn't expect to get as much out of a day or two at several different port stops, but it might help me at least figure out which places I would and wouldn't want to spend a full vacation in the future. :-)