The more gigabytes (GB) you have, the more you can store – from from apps, photos, books, movies and more.
A 16 GB model may be ideal if you have a small music collection and don't download many movies, and want to primarily use the iPad for browsing the Internet.
Choose a 32 GB or 64 GB model if you have a large music library or you download a lot of large apps or HD movies.
Of course, it's always good to anticipate how much storage you'll need in the future as well.