If you plan on using it for magazines and videos, bigger is better. It's too easy to fill up my 64GB iPad. Keeping a year of any given monthly magazine will suck that up quickly. Subscribe to 3 or 4 magazines and you've got some space issues.
I also keep almost all of my photos on here plus a lot of music and a few videos. If Apple makes something with storage, I will find a way to fill it up. Tis why I regret my decision to get a 16GB iPhone 4S.