Here's a little bit of info to keep in mind when picking up a Vita: games can only save data either on internal storage or a memory card, not both. Vita users do not have a choice of where to save data so you must adhere to a game's recording method.
If a game requires a memory card, it's likely that card is used to keep all sorts of data like in-game progress, download content, or to install Live Area features. In fact, games that need memory cards won't boot up without a card inserted into the console.
PlayStation Vita launches worldwide on February 22.