When it comes to devices like the Steam Deck, Asus ROG Ally, Lenovo Legion Go, and any of the other best gaming handhelds, they're all fantastic at playing games. No matter the operating system, once you're in a game, it runs, and that's part of what makes them excellent devices. However, they differ in operating systems, with most gaming handhelds running Windows. When it comes to the Steam Deck, though, it runs Linux, bucking the trend of everyone else in the industry.
If you're looking to pick up a gaming handheld, you can't really go wrong with most of them, but these are the reasons I believe Linux is better suited to gaming handhelds than Windows.
1 Everything you need, nothing you don't
Linux is open source
Gaming handhelds are bona fide laptops with controllers built-in, but they're designed to be more portable, smaller, and built for a specific purpose. Windows, however, is not designed to be modified heavily, and that causes problems for OEMs who are putting together a gaming handheld.
Regarding the Steam Deck, Valve has built a completely custom software stack on top of Arch Linux, with its own SteamOS desktop environment, packages, and translation layer in the form of Proton. Linux is open source, and Valve can do whatever it wants with it and truly make it its own operating system. With Windows, OEMs are at the behest of Microsoft and the things they are allowed to change.
Because of these limitations, companies like Lenovo and Asus have created Legion Space and Armory Crate SE respectively, and they serve as band-aids placed over Windows to make it a little bit better of a handheld experience. They just can't replace an integrated experience like the Steam Deck has, though.
2 Better performance, lighter overheads
Windows is a pretty bloated OS
While you can install Windows on the Steam Deck, something interesting that users have noticed is that some games will run worse on Windows than on Linux, including titles such as Elden Ring. This is partially down to how lightweight SteamOS is, with fewer overheads and multiple tweaks made specifically for gamers.
With that, you also get reduced power draw, though that's also partially down to the hardware that Valve includes. Special care can be taken towards system processes to ensure that they don't sip at too many resources, improving performance and battery life.
3 A hidden desktop experience
You never need to use it if you don't want to
If you boot up a Steam Deck, you can go your whole life using it without even touching the desktop. You can install your games, launch them, and browse the store or community pages all from the gaming UI, and you never even have to think about there being any kind of desktop like on a computer. That's a big plus for people who just want a gaming device that works.
While I'm more than comfortable with Windows, I find that the Steam Deck is incredibly easy to use, and part of that is thanks to the UI. I don't need to tap on the screen or try to click small, finicky buttons on-screen to launch my games or change a setting, it's all just there. Valve has a massive advantage with SteamOS, thanks to that, and I absolutely love it.
4 Never worry about drivers
Play and forget
When it comes to gaming handhelds, I have run into numerous problems with drivers. In the case of devices like the Lenovo Legion Go, I had a pretty rough time trying to deal with drivers. I eventually found the link to download them on Lenovo's site, but for other devices, I've had similar problems. Asus has a pretty good built-in driver management system in Armory Crate SE, but Ayaneo's attempts at driver management also usually require manually downloading files.
However, when it comes to the Steam Deck, it just... works. Out of the box, you'll get SteamOS updates that handle all of that for you, and you never need to venture into any kind of application to install drivers and other software if you don't want to. It doesn't restrict what you can do either, because as already mentioned, there's a desktop mode still available if you want to make changes and other tweaks to your SteamOS software.
5 Modify it to your heart's content
Linux puts tools in your hands
If you have a Deck, you might be familiar with the plugin loader Decky. Because the Steam Deck is based on Linux, you can do basically anything you want to the system and make any modifications that you want. You can completely break your Linux install, too, if you're not careful, but you can also make any system changes that you can dream of if you'd like to.
You, again, don't need to use any of those tools if you want to, but it gives the users back control if they want it. You can optimize any aspect of the device for whatever you want, and nothing is stopping you from focusing hardcore on fantastic performance at the expense of your hardware. You can go the opposite route, too, and limit performance while achieving better battery life, and there's nothing there to stop you, either.
You're not limited to Deck-specific mods either, you can do whatever you want. Any Linux tweaks are fair game, and the world is your oyster when it comes to doing whatever you want on a Linux machine.
Linux is the best option but requires more work for OEMs
If you're a developer at Asus or Lenovo, there are benefits to using Windows, but they're primarily related to the time and money that simply using Windows can save companies. Valve has built its own SteamOS versus just using a Windows install out of the box, and other companies then took that saved development time and put it into their software that runs on top of Windows. Valve had a bit of a head start with its Steam Machines from years ago, but by and large, there's still a significant amount more time required at the start.
On top of that, some games will never run on Linux, no matter what. Games like Call of Duty with a custom anti-cheat won't run, and that's a symptom of how open Linux is. With an open operating system like Linux, cheats can be packaged in the kernel and hidden from running processes, and there's not a lot they can do about it. For those games, Windows is a must. That can be a non-negotiable stance for some people, depending on the target market of your handheld.
Aside from those, Linux has truly been shown to be a better gaming operating system overall when it comes to handhelds. With Windows 12 coming next year, Microsoft will likely improve things significantly, but until then, gaming on Windows handhelds will continue to be a bit of a mess.