I'm using about 22 GB on my iPhone 4 and I don't make any attempts to conserve space. I could easily get by on 16. I would just remove a bunch of the movies I have synced onto it. The 32 will be nice if you want to sync a lot of movies at a time or do a lot of HD video recording. If you have the extra $100 available, I'd say go for the 32 and you won't even have to think about storage space. If you want to save some money, 16 will be good but you might have to be a little conservative with videos.