should I get a 32 gb iPad mini 2 or a 16 gb iPad mini 4?

Next Wednesday's my birthday and I can only afford these two models. First of all I need to tell you I own a 128 gb iPhone 6 where all my music is. I don't play any games, I just occasionally play a couple of them. I'm a sucker for touch id as I get really paranoid of people guessing my pin number, and I'm way too lazy to have a long password/pin number. I plan on using it to read college books and for social networking. Which one should I get?