Why did Revolutionary France annex Rome and Croatia, but sattelite other regions?

For Revolutionary France, the main goal was exportation of The Revolution, but that changes under Napoleon and his Empire. Under Napoleon, non French Land had one of three purposes: direct annexation by France to include both its trade and taxes but also their manpower; indirect buffer states that were semi autonomous (such as the Grand Duchy of Warsaw) or the temporary Kingdom of Holland; and finally direct land grabs that were gifts to allies (such as Tyrol to the Kingdom of Bavaria or Galacia to the Duchy of Warsaw). As such, the purpose of every land grab had reason or need.

Rome is a continuation of this as the Papacy had long been a thorn into the side of France well after the Coronation of Napoleon in 1804 or even the Concordat (1801) which was very important to the peace in the Vendée and other more conservative and rural parts of France. However with long support against Napoleon would turn against the Pope and the Papal States would be annexed by France directly in 1808.

Croatia however is odd. Obtained by France in 1806 as punishment for the War of the Third Coalition, Croatia is a borderland that offers little to France but has more benefit to the major powers in the area m, The Austrian and Ottoman Empires. As a result, this little strip of land between the two would become the Duchy of Ragusa under Auguste de Marmont. The Duchy would be modernized under Marmont whom reportedly built the first roads in the area since the Roman Empire. However beyond the denial of land, the Duchy of Ragusa (Croatia) would offer little other than an observation post for both the Ottoman and Austrian Empires.

On the side, in 1814, Marmont would surrender Paris to the Allies as part of a deal, causing his name to be tied with treason and treachery. Ragusade would enter French as a phrase to signify treason while raguser would enter French to mean "a cheater".

Other satalites like Warsaw or Holland would be buffers against larger and more dangerous enemies but trusted to be able to last on their own. The problem is that semi autonomous is more autonomous than direct control, leading to problems. By 1810, Napoleon would be at odds with Louis Bonaparte and would revoke the Kingdom away from his brother, directly taking control of the kingdom but not the crown. Conversely, Pointaoski, whom was effectively the ruler of the Duchy of Warsaw proved to be an able and honest servant, leading a remarkable defense of Poland in 1809 against Austrian forces.

The difference is effectively that of practical use.