Those are all good points, Tom. I guess I'm thinking as someone who has already resorted to the cloud for photos and music, and after that there's not much that can take up the free space on a 64GB phone.

Between Google Photos and Music, you can store as little or as much on the device as you want, and Apple's services make that possible too. At that point, it seems to become more of a question of how much time you're going to have between WiFi connections to upload everything (unless you have an unlimited data plan). I have no doubt that personally I would be perfectly fine with a 32GB phone and not really need anything more than that. I might get my wife a 64GB model, though.