I prefer Android, but I can understand why people would like iPhones.
-Ecosystem: This cannot be understated, Apple has some of the most seamless integration on all their devices. Being able to make phone calls through your phone and watch as well as receiving texts through your watch and Mac is super cool.
-The functionality: All Apple devices not just phones work straight outta of the box with no major hardware or software issues, you'll never have to worry about any bloatware.
-The cameras: for the longest time iPhone cameras have always been in the upper echelon, rivaling some DSLRs. This feature makes people just buy it.
- Apple support: So long as your warranty is active like apple care, Apple will help you all the way in fixing your devices. Samsung and some other phones have crummy supports as the companies are global.
There are other reasons, but these just are some.
Up to you how "recent" you want the model to be. I'd just go through your carrier for any promotions or discounts on iPhone.