So I've reached Oerba, and I'm very confused about all the new level 1 components. I was under the impression I could go back and use these on freshly re-caught monsters, and end up with higher stats. But using all Mana Drops on Cait Sith for example, has him capping at level 15 with less magic than just using a normal potent drop.
Cait Sith is a late bloomer, if you look at the monster growths document you'll see he gains the same magic through levels 1-15 whether on potent or on mana, so for those levels it's best to use potent. The major differences between mana and potent come in during the level 5 crystarium (since he's a late bloomer). Now the reason why his potent magic is higher than his mana magic for the same level and stat gains would be due to his starting stats. Your old Cait Sith probably had a higher starting magic than your new one.