iPhone 5s - iOS 8.2 (Feb 2015-Sep 2016): got it after the 6 came out because of the size, loved it. Battery life was paltry, however. Currently in a drawer, on iOS 8, with a broken screen after I dropped a powerbank on it.
iPhone 6s - iOS 9.3.3 (Sep 2016-Apr 2017, Feb 2018-Aug 2019): My favourite iPhone ever. lightning fast, significantly better battery life, headphone jack, I couldn’t ask for anything more. Tried a 6 Plus, loved the battery life, got a 7+ in April 2017. Went back to it in 2018 because of the 7+ issue. Used by a family member until recently, destroyed into oblivion and uselessness by Apple after the infamous A9 activation bug on iOS 9 which forced it into iOS 13. Currently in a drawer.
iPhone 7+ - iOS 10.2 (Apr 2017 - Feb 2018): Got it due to battery life, like I said. Came with a broken camera and some odd hardware glitch that presented itself in the form of weird glitches and crashes throughout some native apps. Used it for almost a year, got tired of the glitches and went back to the 6s. Traded in to Apple for an iPhone Xʀ.
iPhone 5c - iOS 9.3.2 - iOS 10.3.3 (Mar 2018 - Aug 2021): got it as a second phone alongside the 6s, then the Xʀ. I have no idea how I put up with that thing, though. Forcibly updated by Apple from the pretty bad iOS 9 to the unusable iOS 10 after it bootlooped. Currently in a drawer.
iPhone Xʀ - iOS 12.3.1 (Aug 2019 - current): My current iPhone. I love it. Battery life and performance are flawless on iOS 12, but my favourite iPhone ever is still the 6s, which…
iPhone 6s - iOS 10.0 (Aug 2021 - present): Got this from a family member to replace the unusable 5c as a second phone. My favourite iPhone, ever, no question. Currently in use as a second phone.