If you currently never take advantage of the Mini's extra portability, the only other reason to get one is if you tend to read on it one handed. We have both the Air and Mini in our house, and when I was trying to decide the same thing you are, I tried my husband's Air. It only took me about ten minutes to realize that I liked being able to hold the Mini in one hand without having to prop it on something, and that when I did prop it on my leg, etc., I tended to use it in positions that just weren't as comfortable with the heavier, larger Air.
If that's not an issue for you, then the Air is probably your best choice. For me, I bought a Mini 2, and I'm generally very happy with it.