I could type faster using T9 on a 10-key flip phone than I can on an iPhone today. On Android I used SwiftKey for many years and would bet I'm fastest on that, but I decided to try an iPhone 6S and it seems like a huge step back regarding input. I still can't believe they don't have a swype-like input method.
iOS supports third-party keyboards since, like, 8th edition. Exactly what made iPhone acceptable to me.
Not that I'm too happy with it: for some reason my SwiftKey's gesture-recognizing algorithm seems to be getting worse over time, while next-word prediction becomes better.
