I'm looking to close a deal on an iPhone. What I am having difficulty understanding is the difference between 16GB and 32GB. When does it matter if you have 32GB and 16GB?

I understand, of course, the technical difference (free space capacity on the internal storage). As a casual smartphone user (have an Android but don't have many apps on it), and a mobile developer, I'm not sure I need 32GB. (I think my Android phone as 8GB, and I'm not using more than half.)

So when does it really matter? What are the "use-cases," if you will, for someone needing or using 32GB but not 16GB?

I'm also not planning to get a data plan, if that matters.