More information here than on the Holland America thread, so I would be inclined to take a taxi from Rotterdam port to the Rotterdam Centraal station and train to Amsterdam Centraal station. If you can manage your one checked bag and one carry on to/from the ship then there is not reason to not use the train.
If you take the transfer to AMS it will probably be about €45 and a taxi from AMS to central Amsterdam will probably cost you about €70, so to me it is a 'no brainer' to go to Rotterdam Centraal and train.