My iPhone 5s has finally given up the ghost. In the past, I've had good luck and saved some money by buying a used iPhone when I have the need to upgrade. Right now, I'm looking at a few choices: iPhone SE/iPhone 6s (used in good condition ranges $150-$200) or an iPhone 7 ($250-$300). The iPhone 8 seems to be too expensive for me even used at this point. I'm wondering what people feel is the sweet spot. I'd like the phone to get OS support for at least two more years. Is there anything in particular technical reason to go with the iPhone 7 over the SE/6s from that standpoiint? I'm still satisfied with the performance of the 5s and so I'm not particularly concerned with speed improvements. Thank you!