I don't have much experience with iOS products, but I recall early in smartphone history being flabbergasted by the lack of basic affordances like a notification bar, or quick settings (eg to switch wifi on/off). I'd imagine both UIs are vastly different now, so I don't think that these examples are directly relevant. But I heard so much in those days about how iOS's UI was vastly superior and was so shocked by my first introduction to it, that I remain baseline skeptical of claims that it's objectively better than Android. People just seem too blinded to realize that their personal preference isn't a universal measure of quality. (This paragraph is mostly in response to the fact that the GP comment is so downvoted for saying "I prefer Android's UI")

As far as picking practical examples, my lack of familiarity with iOS means some of these may be obsolete, but some obvious ones that come to mind:

1) Is iOS multitasking still as poor as it used to be? Eg, are split-screen apps on the iPhone still impossible?

2) Are homescreen widgets still impossible on iOS?

3) Are you still forced to open (eg) app links with lower-quality off-brand apps like Apple Maps, or can you set your preferred app the first time you open a link of a certain type?

I'm not even going very far afield here, as I'm only picking things that a) I know iOS had a feature gap in at some point and b) I would trip over at least weekly were my OS to have these issues. I'd imagine that one could do a little research and come up with more such examples (as well as examples where iOS's UI is superior to Android's).