186ppi is designed for 1.5×, an uncomfortable space that makes perfection difficult-to-impossible, yet seems to have become unreasonably popular, given how poorly everything but Windows tends to handle it. (Microsoft have always had real fractional scaling; Apple doesn’t support it at all, downsampling; X11 is a total mess; Wayland is finally getting decent fractional scaling.)
Apple's HiDPI is "2x scaled" on Retina and >= 4k displays. But you can still pick a virtual resolution that isn't exactly 0.5x your display's native resolution, and it will look great.
For example my external monitor is 3840x2160, and has a default virtual resolution of "1920x1080", but I run it at "2304x1296". My 14" MBP display has a default virtual resolution of "1512x982", but I run it at "1352x878". Neither looks scaled, neither has a slow display, weird fonts or weird graphics. I never even really think about it. In other words, light years beyond the experience on Ubuntu and on Windows.
Your displays are high enough resolution that you may not notice the compromises being made, especially if you don’t get an opportunity to compare it with real fractional rendering, but the compromises are real, and pretty bad at lower resolutions. Pixel-perfect lines are unattainable to you, and that matters a lot in some things. And you might be shocked at how much crisper and better old, subpixel-enabled text rendering is on that same display.
Apple was in the position to do it right, better than anyone else. They decided deliberately to do it badly; they bet big on taking typical resolutions high enough that downsampling isn’t normally needed (though they shipped hardware that always needed such downsampling for some years!), and isn’t so painful when it is needed; and they’ve largely got away with it. I still disagree with them.
As for 1352×878, what on earth is that number, for a native 3024×1964 panel!? 2.237. It’s like they’re gloating about not caring about bad numbers and how terribly inconsistent they’re going to make single-pixel lines.
Do you have a test case where I can see this in action?
As for rendering of text, there is definitely antialiasing in play. Subpixel rendering is no longer used, but I don't think you need it at these resolutions anyway. I'm not even sure what the subpixel arrangement is of my display (is it neat columns of R -> G -> B, or larger R and B with smaller but more numerous G? At 250-some PPI, the pixels are too small to notice or care!). But, I agree that if I was using my old 1920x1200 monitor I would miss it.
1.5x looks ok mostly (though fractional pixels can cause issues in a few circumstances), but across platforms nothing is handled as well as 2x, 3x, etc is. I have a 1.5x laptop and wish it were either 1x or 2x.
Using a lower preset than this is trading PPI for screen real estate. I don't think that's reasonable to introduce into the equation here. Yes, you match the relative size of display elements by virtue of (potentially!) being closer to the screen, but in turn you put more of the screen into your periphery, just like with a monitor or a TV. I don't think that's a fair comparison at all. An immersive distance (40° hfov) for this display is at 37.1 cm (a foot and a bit) - I think that's about as close as one gets to their laptops typically already. This is pretty much the same field of view you'd ideally have at your monitor and TV too, so either you use this same preset on all of them, or we're not comparing apples to apples. Or you just really like to get closer to your laptop specifically, I suppose.
This might sound like a nitpick but I really don't mean it to be. These are proper well defined concepts and terms, so let's use them.
The bottom line is that I work with text (source code) all day long and I would rather read from a display with laser printer quality than one where I can see the pixels like an old dot matrix printer. Some displays are getting close to 300 DPI which is like a laser printer from 35 years ago.
The brief version is that if someone has a screen real estate concern, they need to look for the PPI, but if they have a visual quality concern, they need to look for the PPD.
Maybe it will be elucidating if I describe a scenario where you will have low PPI but high PPD at the same time.
Consider a 48" 4K TV (where 4K is really just UHD, so 3840x2160). Such a display will have 91.79 PPI of pixel density, which is below even standard PPI (that being 96 PPI, as mentioned).
Despite this, the visual quality will be generally excellent: at the fairly typical and widely recommended 40° degree horizontal field of view, you're looking at 3840 / 40 = 96 PPD, well in excess of the original Retina standard (60 PPD), which is really just the 20/20 visual acuity measure. Hope this is insightful.
It also introduces an element of uncertainty: as you say, you can't specify a laptop screen's PPD since that's dependent on viewing distance. But that's exactly the problem: it's dependent on viewing distance. Some people hunch over and look at their laptops up close and personal, others have it on a stand at a reasonable height and distance. To use PPI is to intentionally mask over this uncertainty, and start using ballpark measures people may or may not agree with without knowing.
To put it in context, for this display, "Retina resolution" (60 PPD), i.e. the 20/20 visual acuity threshold, is passed when viewed from 47.09 cm (18.54 inches, so basically a feet and a half). I don't know about you, but I think this is a very reasonable distance to view your laptop from, even if it's just 12.2" in diagonal. It corresponds to a horizontal field of view of 32°.
> the 20/20 visual acuity threshold
The acuity threshold for random blobs of light.
The threshold for sharp edges is much finer, and the things we put on computer displays have a lot of sharp edges. https://en.wikipedia.org/wiki/Hyperacuity
It pretty much has that though? 1920x1200 at 12.2" is 185.59 PPI. Standard DPI (PPI) is 96. HiDPI to my knowledge isn't properly defined, but the usual convention is either double that or just more than that - the latter criteria this display definitely clears, and the former (192 PPI) is super super close, to the extent that I'd call it cleared for sure.
It's pretty hard to not clear at least the latter criteria on a laptop anyways. You'd see that on 720p and 768p units from like a decade or two ago.