The most formidable galleon in the game comes under the title "The Black Ship". Originally, it is controlled by the faction European Traders. When it comes into your faction's line of sight, a message will be sent informing you of its arrival, urging you to capture it before someone else does. The Black Ship has powerful cannons at its disposal (with a morale-damaging effect), as well as a crew full of gunmen.
Other galleons (Nanban Trade Ships) can only be acquired by or captured from Christian factions. The reason is that they can only be recruited from Nanban Quarters, an upgraded version of Nanban Trading Ports. It should be noted that no matter what religion your faction is, if you come into possession of a galleon you have the ability to repair it at any one of your ports.
Between the two types, The Black Ship is the more powerful in crew size and number of cannons, but you can get a potentially unlimited number of Nanban Trade Ships if you have the right resources.