Well I bought the fort and thought it was a very good deal for 40 euros.
Then again, I dont have other sets that big. the lighthouse does seem to be a bigger structure, but it seems to have barely any accesoires while this fort is filled with them.
The way I see it is, the fort offers a wall and tower, plenty of docking space, and also a treasury and jail. And along with that there is a treasure chest with gold, a table and stool, a bottle of rum, a basket with potatos, a barrel, two small barrels, handcuffs, keys, a map, a sack of grain, a torch and of course a cannon and three well armed and detailed clickies.
All the furniture and supplies can easily be used for any historic set up, never hurts having more of it around.