I voted on the Skull's eye Schooner, it has a broadside of 4 while the Black Seas Barracuda has only 2,
that means that the SES can fire 4 cannonballs at once while the BSB can only fire 2 (in one direction)
so the SES would damage the BSB more.
Furthermore, the SES is a Galleon so it would probably be faster than the BSB but that's just a detail.
though I like the BSB more, the Skull's Eye Schooner is the winner in a cannonbattle
you are right about the sterncastle but my SES never broke in two at its midsection, I think the amount of guns IN ONE DIRECTION is most important in a battle