I have an iPhone 7 which I bought less than a year ago so I'm a late adopter.
I ended up moving because I was missing messages on Whatsapp because notifications were sketchy on every Android phone I could get my hands on to try. A few friends with iPhones said it worked fine on theirs so I made the jump - needless to say, the same problem spans the app on both platforms...
Overall it's a pretty good phone though, I'm pleased with it with the exception of one killer for me - you can't set your default browser on it anything that opens a web page always opens it in safari and I don't like safari at all. This for me I think will probably stop me buying another iPhone.
Battery life and charging speed are a step backwards too.