I ditched my laptop for a pocketable mini PC and a pair of AR glasses — here’s what happened

I've thought about doing this too, with a very similar setup.

Larger FOV for your screen than anything else portable. Potentially more power efficient too, as you don't blast light everywhere to get a tiny bit into an eye. Can be used in very bright conditions, like outdoors on a bright summer day, without issues. More comfortable to use in some other orientations --- I use a split ergo keyboard with my laptop when lying back in a recliner or on a couch, lets my hands not be jammed in front of me and obstructing my views of the screen, but an HMD is even more flexible.

Laptops have limited hardware customizability, so it's really the only route other than carrying a portable display if you want more control over the PC hardware. Want a 100Wh battery or larger? Non-soldered memory and more of it? More expansion ports or storage slots? Moving the hot-and-noisy stuff beneath the table instead of beneath your hands? For the form factor: have airflow vents that aren't on the bottom and covered up when on a lap (ironically, "laptop"), chest, couch, or bed? If you're a woman and want to use the thing on your belly while lying down, not having your breasts in between your eyes and the screen? For anyone, not having their hands in the way?

Laptops have a lot of limitations as to input devices. Do you want a Trackpoint? You're limited to a very few models of laptop. Trackball? Few laptops and it has to be very small. A trackpad with three physical buttons? Very few laptops on offer make that an option. Particular about your keyboard layout? If you're getting external hardware, there's a cornucopia of options, and you can mix and match as you'd like. Yeah, you can also do this with laptops and a stand and a docking station and external hardware, if you're aiming for use at a particular desk, but that's not really suitable for a couch, say.

The privacy is nice -- and I don't think that that reasonably can be reduced to looking at porn, which I assume most people aren't going to want to do in public anyway, for obvious reasons. I can throw a password list up onscreen, don't need to deal with those inane "hide your password as you type it" things that try to mitigate privacy issues with people using computers in public places.

Problem is that at least today, wearing HMDs is not as comfortable and sharp as looking at a display. Easy to get something slightly blurry if it's not perfectly aligned. My HMD tends to fog up, though the Xreal thing in the article has more airflow and it's probably less of an issue. Also, VR goggles and headphones tend to compete for the same spot around the ears --- circumaural headphones need to seal there, so you may need to accept whatever sound, if any, the HMD can provide. You have less awareness of your surroundings, which matters in some situations.

A lot of work has gone into making laptops particularly low power, and if you build your own system, some of that is on you, to pay attention to component power consumption.

Also, I couldn't find a way to get some kind of external battery to be treated by Linux as a power_supply class device, which lets Linux do things like automatically hibernate when power gets critical and use nice in-UI reporting of low battery. On the power source side, USB PD power banks, which it would seem would be a good solution, technically have the ability to report a battery level but AFAICT do not actually do this, or even present themselves as visible devices on the USB tree. You could probably work something up yourself with a modular battery bank --- at the very least, even if Linux can't use it as a power_supply device, NUT can be rigged up to treat some hardware that you can put on a modular battery bank as a UPS, which accomplishes some of the same stuff, like auto-shutdown. And a modular battery bank is pretty user-configurable. But...that's not necessarily all that portable.

I would definitely do this instead of a laptop if they managed to get HMDs to the point where I'd be willing to dump my displays and go all HMDs. We aren't there yet, though.