And if you're looking to make the most out of this system, you need to know about ABI, how it affects growth, and how you can raise it. Your Digimons' personalities do matter, but they affect things differently from what you might expect. There's more to this than you might think. You can change one's personality via Patch items at any time, and you'll find it's more than worth it.
There are a total of 8 personalities your Digimon can have, but you're not tied to a particular one per Digimon.