I think the biggest factor is animations. Switching from an old Android phone (with animations turned off) to a brand new iOS (at least at the time) felt like a

I think the biggest factor is animations. Switching from an old Android phone (with animations turned off) to a brand new iOS (at least at the time) felt like a downgrade at first, because every interaction with the UI was so much slower than I was used to. Clicking a button didn't actually make the thing I wanted to appear immediately, but instead it faded in over 200ms or something, making the phone that had 10x better specs feel much slower.