For simplicity's sake, let's assume there are no contracts and subsidies, and that any purchase will be done off the Apple Store. Moreover, because I'm not in the United States, there is no AppleCare+ or the upgrade program. A friend recently asked me for smartphone recommendations. She's interested in iOS this time around, and her uses are basic - calling, texting, social media, web browsing, photography. It got me thinking - would it make more sense to buy the iPhone 5S, which is still available brand new, and update to whatever is the entry-level model every 2-3 years, or would it make more sense to buy the latest flagship model every 4-5 years?