Go to the store (Apple Store, Best Buy, w/e) and check out each one. I started with a Nexus 7 and while it was a great tablet, I simply did not like the size. It was good for reading but I would rather use an e-ink reader for long reading sessions. The Air is not much more uncomfortable for reading and it is so much better for displaying anything large screen. I read a lot of comics and while it was passable on the N7, it is ~great~ on the Air's screen. For me, I will never buy a 7'' range tablet again. It isn't as if they are bad machines though and they have tons of fans so really only you can answer what size is most comfortable for you.
I use a large phone too, which is why I'm stuck on a Note 3 right now since the 6+ wasn't out yet when my last upgrade came through lol