First, let me clearly qualify that I am in no way a fan of, nor advocate of notches. I don’t enjoy them and the resulting asymmetry mildly triggers some level of OCD in my brain. That being said, how Apple utilizes it bothers me the least and there is actually a small bit of functional advantage vs. how the phone would have to be designed/implemented without using one. The notch on the Pixel 3 XL is just absurd. Again, this is just my own personal perspective.
Speaking specifically in regard’s to the iPhone’s implementation, the notch affords a space for all the sensors they need for Face ID, the proximity sensor and front facing camera. The alternative would be to just have them housed in a full top bezel. That would mean either a larger device to have the same amount of usable screen space or less usable display area. The information presently in the ears would be part of the status bar and need to be pushed down into the top of full display area, meaning less space usable by apps, home screens, etc—in both portrait and landscape. I might mean a loss of only .3 inches but it would be less.
The hallmark feature of the iPhone that I love is the absence of a chin. I still don’t understand why no other manufacturer has been able to pull this design element off. So as I see it, assuming an implementation of the exact same amount of usable display space, we have 3 display design options (I’m not including designs like the Find X or Nex as I find them functionally compromised)—a larger iPhone with no chin but a full top bezel, an even larger iPhone with matching full top and bottom bezels (a la Note or Galaxy, for symmetry, of course ), or the current design, smallest overall of the 3 options, with no chin and a notch. I personally am glad Apple choose the implementation that they did. For my preference, it’s the best fit.
The only screen you're gaining with any notch, including the iPhone's, is the size of the operating system's status bar. That's it. So whatever the size of the status bar of iOS is, that's all you're gaining. I don't believe it's even .3 inches. I think it's .1 inch maybe...?
And this .1 inch gain is only in portrait mode. In landscape, you either have the ears blacked out (it's not always necessarily black, the point is the ears get filled out) or you go truly full screen and the notch actually intrudes on your viewing. In the latter scenario, you actually lose screen space.
And that's it.
There's no sound argument for the notch, whether it houses good tech in it or not (you can still house good tech in a regular ol' bezel) or whether one uses the argument of "you get more screen space." The screen space argument is only true in the most basic meaning. You're only gaining about .1 inches or so of screen space. The trade-offs for that are not worth it.
Use of these arguments in favor of a notch come from people who have grossly miscalculated the pros and cons. And they're typically users who have no choice but to accept the notch in their device. Not describing you here. I know you're not a fan of the notch either. Just saying, there is no good argument for it no matter how it's spun.