ELI5: Just how different are smartphones?

So, Im curious about something. I get that Android, Windows and Appel all offer different apps.

But my question is this, when Im reading about "Flagship models", "completely over hauled" and some costing £300+ and others costing £80.

Is there ever any major difference. I mean, 100% noticable. Sure, battery life may be better, it may run faster or get a better signal.

But with what, hundreds of thousands of models out there, what was the last super major gamechanger?

And if that isnt clear enough for you? Reword it and make it an answerable question >_>.