With the 32 GB model gone, there's really no excuse not to get the 64 GB model. The 16 GB one offers no value.
"no" value? It is an iPhone. It can do everything the other models can do, just it holds less.
My 16 GB iPhone right now has 2.9 GB available. And that's with 2.1 GB in my camera roll. More than enough to record plenty of additional video.
I see no reason to spend another $100 for capacity that I won't use very often.
Oh, yeah, when I'm going on a long trip, I might want to load it up to the max with music/movies. I might even delete a large app to fit one more movie on. But as infrequently as I use that, it's not worth the extra $100.
And 2-3 years down the line when I go to sell it, the extra capacity CERTAINLY won't get me an extra $100.
Once the iPhone has the ability to zoom at least 5x without losing *ANY* picture/video quality, *THEN* I might be interested in more storage, as it would be able to replace my "point and shoot" camera entirely.
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Aside from that, most people tend to hold on to old pictures, videos, text messages, and Facetime conversations. So each time you get a new phone you've got another year or two worth of content that needs to be kept around if you don't want to delete it.
Pictures and videos are supposed to not use up storage with iCloud Photo Library in iOS 8.
Text messages can be set to "expire", so that the attachments don't take up space.
FaceTime has *EVER* taken up space after-the-fact. It's live-only, no recordings.
And text messages (and the text entries regarding phone calls and FaceTime calls,) don't take up much room at all.