I actually own a steam deck! Its a great system, that runs on Linux, so there is a little bit of tinkering and buyers awareness to get through as not all games on steam run on it easily.
The catalogue compatible with just one tap/click is still growing, but you still have to use the proton tool before launching a game that is windows based. Some online games are also protected with some anti cheat software that may or not stop you from playing your favorite online games. Its also a handheld, so unless you plan on connecting the steam deck to a screen and bringing out a keyboard for your keyboard based game, you are going to have a bad time. (Note, there is a virtual keyboard thay pops up if need to enter some text occasionally).
The thing that attracted me to the deck, is the fact that you can actually launch the steam deck in desktop mode, that gives you access to a fully functioning linux system. There, you can also download your games from other launchers/stores and link them to your steam game library and access them through the non desktop mode.
This means that with some more tinkering (kinda alot actually, i wont lie), you can turn the steam deck into the ultimate emulator for any switch/some ps3 games and lower (as in raw processing power, so gameboy, gamecube, ps1, ps2, xbox etc) on the go. You also get a rather powerful computer for an amazing price point,at the cost of an hdmi/usb/ethernet dongle or dock. Since its a computer in the shape of a hanheld console, you can dualboot windows if you wanted.
The other very cool thing, is that you can use steam to stream your games from your gaming pc right to your tv by using your steam deck as a streaming game console, which is amazing and in the end extends your desk PC capacity to offer the best couch gaming experience with no drawbacks if it wasnt for the whole ensemble price. Also the trackpads are a very cool addition to the gamepad layout, amd it has extra buttons on the back! Since it has bluetooth, you can also just get a controller and let it chill next to your tv.
You can configure it the way you want, you can apply cool mods, change components within pretty easily (some ppl buy the cheapest version then upgrade the hardware to save money!) And since its a steam hardware product that has successfully proven itself to enough ppl, the support its gonna be getting is very exciting.
To me the problem of the Steam deck is the time and tinkering that it requires to setup this perfect machine, but its a new system, and emulation is in a gray zone legally in many countries so it will probably always require some amount of tinkering. (There are vids online that take you through it, its absolutely doable but can be a barrier for some newcomers) You can manage well the battery, but it drains rather fast. If you dont like steam, idk if this product is right for you, but you can install windows or another linux distro if youd like. (Level 3 tinkering right there)
I love my steam deck, and actually do work on it occasionally, which got me more comfy with the linux ecosystem (but this is about just using linux as an operating system so im gonna stop here). Its the best for the indie games on steam as long as they have gamepad support and are compatible with or without the proton tool.
Now for the other handheld PCs, I cant speak. I heard that some are very powerful, more than the steam deck by quite alot, however imo they are held back by being run on windows, an Operating System that is not made for such a device, but will absolutely get you through the anti cheat headaches that a steam deck might have.
They also have a 1080 p screen for the fancy ones, but this impacts battery.
You can install chimera OS or Bazzite if you want the linux experience, and the Steam Os (on the steam deck) is coming soon (its gonna be a while though).
So yeah im gonna stop there cuz i cant stop talking about this thing.
Cap’ain! She’s leaking coolan’ from the s’arboard bow!