In iPhone and iPad use, where does the space usage come from? iPhones and iPads come with varying amounts of space available; iPads offer powers of two from 16G to 128G and the price difference between them offers a substantial amount of other software and services one could afford by saving money on hardware.

What space usage motivates the usage? If there's a 90% full iPad at any amount of storage, what does the bulk of the usage come from? (I'd imagine media like music, photo and video shooting, etc but would rather hear from experts with some experience) Perhaps this is just careful developers at work, but you can get a lot of apps and still see very little space being used so I don't see why I would need anything more than 16 GB with my level of experience.

I'm looking for people with experience running an iOS device at more than 75% full for several months to explain what they've learned and perhaps explain whether they can live with the devices they initially bought or how they would take their current experience to select a new device.
My 64GB iPhone has several hundred apps on it, mostly games, about 9GB of photos/personal videos, 3GB of music, and ~5GB of free space right now. I do have to prune from time to time but it's not too bad.

My 32GB iPad on the other hand...I really wish I had bought the 64GB (the largest at the time). I am constantly having to juggle what games/apps are on there, and that's really what's taking the majority of the space. iPad-specific apps can get huge...even universal apps can. I've seen several 1GB+ games, and have a bunch that are in the 250MB to 500MB range. I have only a fraction of my photo library on there, and no music or videos to speak of.

I am excited by the idea of a 128GB iPhone possibly being introduced Tuesday, and when I have saved for a new iPad I will get at least the 64GB model.