I'm going in-depth with my rant again. Feel free to only read the first paragraph and skip the rest as it's not all a response to the above comment.
Yeah—defaults matter and I'm glad you picked up on what I was getting at. Part of good product design is making good decisions for the end user. Apple has done a satisfactory job at that for years. I wouldn't say excellent, but satisfactory. 16GB, however, after considering the OS, 10-15 apps and a few music playlists comes out to around 8GB of usable space to save photos and videos. Shooting 4k, that means they can record 22 minutes of video whereas the previous default (1080p 30fps) could record 63 minutes. 8MP photos on the iPhone 6 usually average around 2MB/photo. Therefore you could reason that the 12MP photos would be around 50% larger in file size at 3MB.
Taking it a step further I read that live photos will make the file size double, and Apple said that this feature is turned on by default. I agree in principle of turning it on by default as it's a neat feature that brings the photos to life and distinguishes Apple from other device manufacturers. But that makes it 6MB per photo. If a user were to shoot 15 minutes of video and the rest as photos, they could shoot 434 photos. Again, this is running the phone to full capacity (not recommended) and leaves no room for local storage of apps for documents, messages (including received photos and videos), health data, or much of anything else. Realistically we should reduce these numbers by around 20% for real world usage, so 12 minutes of video and 347 photos.
The photos number is probably adequate for basic users but not ideal. Perhaps I'm an outlier, but I just went to my photo library on my Mac and selected September 21, 2014 until today and it said I have taken 2,894 photos/videos in the past year. Even if I'm statistically outside the norm, surely most people will go through more than 347 photos per year. I'm not even very active on social media and rarely take a selfie. I bet many non-tech people could blow past my numbers quickly. I hope Apple makes it apparent to users that it is easy to lower the video quality and turn off live photos. I also think Apple should provide a quality control for photos. I know that you can turn off Live Photos, but for most people simply posting to the web, they could cut their file sizes down by lowering the MP per photo.
There's also iCloud Drive for these people, however uploading 4K videos on slow internet connections (or even fast ones) will take considerable time and could put a drain on their battery—and in some cases even their home internet plans as many today have data caps. My home internet last year was capped at 350GB (which we hit after my wife gave birth to our first child and streamed a lot) and later in the year I went up to the 100Mbps plan which is now capped at 999GB. I believe our entry level plans at the cable company start out at 100-250GB. If they're a streamer adding 4K video uploads to the cloud could push them past their cap—not to mention add a monthly expense. Might as well go for the 64 or 128GB version. However many people don't realize how huge these files are going to be, which again brings me back to my original point. Suck up the extra cost and build-in good defaults. Even 32GB at $249 would be a decent step in the right direction! I see a lot of frustration from users about their iOS devices running out of space. Most people aren't like us tech-educated MacRumors users buying the expensive models. I'd even go as far to say that users see the 64GB number and think "That's a waste if I get THAT much space." I know because I've had people tell me there's no way they need 64GB and go against my recommendation and get the 16GB, only to have me clear off their device within half a year.
