That question is left unanswered. May be that is because the audience won't like the answer...
Nowadays iPhones and flagship Androids have gotten good enough that the pain of switching ecosystems far outweighs any benefit to be gained by switching ecosystems.
Thank heavens. Because we all know how judging phones by letter grades, percentage points, and benchmark scores is so useful.
Not sure I agree. Most people I know ended up with their phone because that's what was popular at the time, or because it was pushed into their face, or it was reasonably inexpensive, or it was what their company handed out. They use it, play games, might use a specific app here and there, and might use the more advanced ecosystem features but more than likely those confuse them. They use it because they're used to it by this point, and not much more. Meaning changing wouldn't be the end of the world.
Personally I have an iPhone (and iPad) and have a good number of apps, though I regularly use very few of them and am enamoured with even less. I'm not necessarily invested in the ecosystem -- I wouldn't mind throwing away most apps I paid for since they were $1 and because I don't even use most of them any more, and the ones I do care about are most likely available on alternative ecosystems. It also doesn't help that my backups in iTunes fail 90% of the time and the bulkiness and slowness of iTunes does not often lead to a positive experience. I'm not saying alternative ecosystems would be all roses, just that this is my experience and that it prevents me from becoming overly attached.
smartphone costs a few thousand dollars to own over a couple of years. Cost of apps is bust a small portion of that cost.
(btw, I'm not at all saying there aren't good replacements, just that you have to learn about which ones these are. The same argument could be made with regards to switching from Android to iOS).