How or why does Linux have a higher performance for you?
A lot of responses and none of them are false but the main reason for the improved gaming performance is DXVK, it translates DirectX 9 and 11 to Vulkan and is used by default on every DX9/DX11 game on Linux when you use Proton.
The Vulkan stack on modern GPUs is much more optimized compared to DX9 and 11. It has gotten so bad that many Windows people use DXVK on Windows to solve performance issues and even Intel uses DXVK (or similar technology) for their Arc GPUs.
I keep wondering why DX development is so fucking slow
not OP but similar situation. My Linux desktop is just more snappy, despite being 5 years old (and the work Win11 laptop brand new). I already have customized with my shortcuts and apps. I don't have to listen to the fan spinning up every time I open a new window (exaggerating a bit, but not much). Also I am not tied to work filters. If I want to read the news online for 5 minutes in a coffee break I don't risk being monitored and potentially evaluated. But really, I've been a Windows and Linux user for 20-odd years. I've always found that Linux installed on the same hardware of Windows is just smoother and faster. Windows is getting so much bloatware (from MS or enterprise apps) that it doesn't even have a fighting chance.
Memory management and file IO is far more efficient in Linux. So much so that I even got better performance in Windows running Debian in a VM for some very file-intensive stuff. And by better performance I mean a factor of about 10.
Also, MORE FILE SYSTEMS! NTFS is crap
Most desktop environments are really efficient at what they do and minimize the background resources they take. Just checked my system and GNOME takes ~350MBs RAM (~700MB including gnome-software) and literally 0.0% CPU, it's insane. I looked up Windows 11 and it seems like it can use up to 4 GBs (!) of RAM all by itself.
It can and will if you let it
My comment isn’t really a viable argument but I’ve been thinking about how an advert for Linux would be:
“The top 500 supercomputers in the world run Linux, don’t you want to feel like having a supercomputer at home? Why wait? Get your Linux for free today!”
Not really to be taken seriously, but if you want a real argument and example:
My laptop is really laggy with windows 10, and it came preinstalled with it. Recently I tried dual-booting Linux and Windows, and Windows was simply too slow. I am so accustomed with Linux’s speed that I wiped Windows off it. Never again.
Probably just down to less stuff running in the background using up CPU cycles. I can't imagine it makes a huge difference, but more than nothing.
Depending on the situation, it actually can make huge differences.  For instance, I built my computer in 2010 it’s 13yrs old now. it can’t run windows 11 and while it can run windows 10 it runs like complete shit. Start up would take forever even on a fresh install, half the time Windows freezes just trying to get to the desktop after a fresh reboot. at idle background processes from windows would leave me running over 50% CPU usage just idling and opening anything like Firefox and Discord at the same time would jump to 100% CPU usage.
On Linux it runs just as good as the day I built it. Startup takes around 30 seconds and I can actually start working the moment I’m on the desktop, no freezing or waiting for background startup processes to finish. I currently at this moment have around 20 workspaces (aka virtual desktops) open across three monitors, within those work spaces is hundreds of tabs open in Firefox, simultaneously playing RuneScape and dwarf fortress. A bunch of terminals, SSH sessions, and other miscellaneous work stuff running. a ton of docker containers running, I also have both discord with a call going and Spotify playing in the background and I am setting at 30% CPU usage with the occasional spike to 50%. I can actually use my computer to do a ton of stuff and have power left over while windows would max out and freeze up just the start up, even on fresh installs. And it’s not just this one old computer, I can consistently see rather large performance differences going from Windows to Linux across the number of different computers. 
I’m on Fedora 38 with I3 WM and a few kde apps, originally installed as 35 and just upgraded since. Before that was arch briefly and before that was debian. 
I went with Fedora because I need my computer to work without issue when it’s time to work and on arch I spent more time tinkering and getting things working then actually working. I still think just plain Debian a solid choice and I use it on a lot of servers but as a desktop, I felt like I ran into a lot of outdated packages. With Fedora I’m getting up-to-date packages yet I have never had an update break the system.  I also prefer DNF and their repository over apt and deb files. It’s all just personal preference though. You just gotta try them all and see what you like!
I appreciate you taking the time to describe why you chose Fedora; now I'm tempted to try it, lol. I'm downloading the 38 Budgie spin now and adding it to the list. (It'll run like shit with apps until I upgrade the RAM on my Macbook, but the minimum hardware reqs are met and I can still look at it and see what it does out of the box.) Thanks!
Good luck on your Linux journey! I’ve never tried the Bungie spin, but Fedora is a very solid distro and I bet it’ll work great. Those MacBooks with Linux are so nice! I ran a 2011 MBP with a mix of plain Debian and Ubuntu for awhile and the battery life on that thing was amazing!
Also, the file system. For the longest time windows used NTFS exclusively, which is (or was) slower than Ext4 (the most widely used on Linux).
I think MS is moving away from NTFS and are going to use a different file system in the near future (maybe even now, I don't know anymore)
They've been talking about replacing NTFS for a long time. 10 years ago they put ReFS in the server builds and.. show of hands anyone using it?
I think they were trying to make ReFS compete with things like zfs but 10 years later it still doesnt support compression, encryption, quotas or booting..
I don't think NTFS is the actual problem, but the Windows VFS layer (or whatever it's called over there).
Running windirstat (or similar programs) is dog-slow on Windows, k4dirstat eats through the same partition quite a bit faster. Getting metadata to sort a directory with what 5000 files by modification time can take minutes in explorer, with Linux it's pretty much instant. minutes. That's not just non-optimised that's abysmal.
How or why does Linux have a higher performance for you?
A lot of responses and none of them are false but the main reason for the improved gaming performance is DXVK, it translates DirectX 9 and 11 to Vulkan and is used by default on every DX9/DX11 game on Linux when you use Proton.
The Vulkan stack on modern GPUs is much more optimized compared to DX9 and 11. It has gotten so bad that many Windows people use DXVK on Windows to solve performance issues and even Intel uses DXVK (or similar technology) for their Arc GPUs.
I keep wondering why DX development is so fucking slow
not OP but similar situation. My Linux desktop is just more snappy, despite being 5 years old (and the work Win11 laptop brand new). I already have customized with my shortcuts and apps. I don't have to listen to the fan spinning up every time I open a new window (exaggerating a bit, but not much). Also I am not tied to work filters. If I want to read the news online for 5 minutes in a coffee break I don't risk being monitored and potentially evaluated. But really, I've been a Windows and Linux user for 20-odd years. I've always found that Linux installed on the same hardware of Windows is just smoother and faster. Windows is getting so much bloatware (from MS or enterprise apps) that it doesn't even have a fighting chance.
Memory management and file IO is far more efficient in Linux. So much so that I even got better performance in Windows running Debian in a VM for some very file-intensive stuff. And by better performance I mean a factor of about 10.
Also, MORE FILE SYSTEMS! NTFS is crap
Most desktop environments are really efficient at what they do and minimize the background resources they take. Just checked my system and GNOME takes ~350MBs RAM (~700MB including gnome-software) and literally 0.0% CPU, it's insane. I looked up Windows 11 and it seems like it can use up to 4 GBs (!) of RAM all by itself.
It can and will if you let it
My comment isn’t really a viable argument but I’ve been thinking about how an advert for Linux would be:
“The top 500 supercomputers in the world run Linux, don’t you want to feel like having a supercomputer at home? Why wait? Get your Linux for free today!”
Not really to be taken seriously, but if you want a real argument and example:
My laptop is really laggy with windows 10, and it came preinstalled with it. Recently I tried dual-booting Linux and Windows, and Windows was simply too slow. I am so accustomed with Linux’s speed that I wiped Windows off it. Never again.
Probably just down to less stuff running in the background using up CPU cycles. I can't imagine it makes a huge difference, but more than nothing.
Depending on the situation, it actually can make huge differences.  For instance, I built my computer in 2010 it’s 13yrs old now. it can’t run windows 11 and while it can run windows 10 it runs like complete shit. Start up would take forever even on a fresh install, half the time Windows freezes just trying to get to the desktop after a fresh reboot. at idle background processes from windows would leave me running over 50% CPU usage just idling and opening anything like Firefox and Discord at the same time would jump to 100% CPU usage.
On Linux it runs just as good as the day I built it. Startup takes around 30 seconds and I can actually start working the moment I’m on the desktop, no freezing or waiting for background startup processes to finish. I currently at this moment have around 20 workspaces (aka virtual desktops) open across three monitors, within those work spaces is hundreds of tabs open in Firefox, simultaneously playing RuneScape and dwarf fortress. A bunch of terminals, SSH sessions, and other miscellaneous work stuff running. a ton of docker containers running, I also have both discord with a call going and Spotify playing in the background and I am setting at 30% CPU usage with the occasional spike to 50%. I can actually use my computer to do a ton of stuff and have power left over while windows would max out and freeze up just the start up, even on fresh installs. And it’s not just this one old computer, I can consistently see rather large performance differences going from Windows to Linux across the number of different computers. 
If I may ask, what distro did you settle on? I'm trying out a handful myself right now.
I’m on Fedora 38 with I3 WM and a few kde apps, originally installed as 35 and just upgraded since. Before that was arch briefly and before that was debian.  I went with Fedora because I need my computer to work without issue when it’s time to work and on arch I spent more time tinkering and getting things working then actually working. I still think just plain Debian a solid choice and I use it on a lot of servers but as a desktop, I felt like I ran into a lot of outdated packages. With Fedora I’m getting up-to-date packages yet I have never had an update break the system.  I also prefer DNF and their repository over apt and deb files. It’s all just personal preference though. You just gotta try them all and see what you like!
I appreciate you taking the time to describe why you chose Fedora; now I'm tempted to try it, lol. I'm downloading the 38 Budgie spin now and adding it to the list. (It'll run like shit with apps until I upgrade the RAM on my Macbook, but the minimum hardware reqs are met and I can still look at it and see what it does out of the box.) Thanks!
Good luck on your Linux journey! I’ve never tried the Bungie spin, but Fedora is a very solid distro and I bet it’ll work great. Those MacBooks with Linux are so nice! I ran a 2011 MBP with a mix of plain Debian and Ubuntu for awhile and the battery life on that thing was amazing!
Also, the file system. For the longest time windows used NTFS exclusively, which is (or was) slower than Ext4 (the most widely used on Linux).
I think MS is moving away from NTFS and are going to use a different file system in the near future (maybe even now, I don't know anymore)
They've been talking about replacing NTFS for a long time. 10 years ago they put ReFS in the server builds and.. show of hands anyone using it?
I think they were trying to make ReFS compete with things like zfs but 10 years later it still doesnt support compression, encryption, quotas or booting..
I don't think NTFS is the actual problem, but the Windows VFS layer (or whatever it's called over there).
Running windirstat (or similar programs) is dog-slow on Windows, k4dirstat eats through the same partition quite a bit faster. Getting metadata to sort a directory with what 5000 files by modification time can take minutes in explorer, with Linux it's pretty much instant. minutes. That's not just non-optimised that's abysmal.