Other than opening up puzzle pieces and being able to progress in the Mii games to get tickets to get hats for your Mii but if you're not into that. Then I say take your Vita instead and get some cool import games or the 64GB memory card while you are there.

What a crazy schedule. Did you take any handhelds to pass the time? You'll find some one. It's good that you are taking it slow you don't want to jump into something to quickly. Believe me your every guy gamer's dream a girl that plays games :)

I would take my 3DS if for no other reason than imagine all the street passes you'll get. Gamewise that's a tough one depending on what kind of games you enjoy. If your into RPG's for sure take Pokemon or Bravely Default. Now that I think about it maybe the Vita would be best just because you could buy games and instantly play them there. Since they are not region locked like the 3DSs. But dem street passes tho! AHH I don't know I'd take both.