1. Package managers are a godsend and there's nothing like them on Windows. Chocolatey is okay, but it's got nothing on Linux pms. This discontinuity between installing and upgrading some applications, other applications, Windows apps, drivers, and system software makes me want to cry.
2. Customization. Man is Windows lame here. Colors on Windows is about all you can do, and it's so limited. I bought the machine I should be able to set it up how I like. There are some deeper ways to theme and adjust things more directly, but they're hard to use and risk breaking your system. On Linux, customization is easy, even on a more pro-default-option DE like GNOME. I just want things to work, and Windows fights me to get it to a usable state.
3. Bloat, telemetry, ads, proprietary garbage, etc, etc, etc. I like FOSS and using FOSS software, and I can use it on Windows, but I have to have so much other stuff too. Debloat scripts exist, but they can only do so much. There's always gonna be something Microsoft owns on the system
4. Complexity and control. Linux is simple. Binaries go in bin, and the settings for them are usually in ~/.config or somewhere in /etc. Want to adjust some obscure setting to fix some issue in a program you installed? Oh go tweak this clear config and explicit setting to fit your hardware or whatever. Easy to fix. On Windows, all the system stuff is not only hidden, it's restricted, and also so many times on Windows when you run into issues the solution is you have to edit *shudder* the registry, or worse you have to do a PC reset. Overtime your system slows and blue screens become more frequent too, and there's nothing you can do. On Linux, you can learn 7 or so folders and understand how your entire system works, keep it maintained, and run it for years. Had a prof in college who was on like a 20yo Gentoo install.
5. Tiling. There are ways to do tiling on Windows, but they're all bad and glitchy. Nothing on Windows comes close to i3, and I can't go back to a non-tiling workflow. Windows wants you to do things the Windows way, and anything outside of that is always lack luster. People talk about Linux balkanization as a problem. It's not. Those people are just ignorant and stupid. No system can ever really fit all use cases, so it's important to support choice. Windows doesn't just promote one way to do things a la GNOME, it actively works against doing things other ways.
6. Programming. Compilers and dev tools on Linux are so much easier to install and set up than on Windows. If you want to program, you've gotta be on Unix/Unix-like
7. Windows weirdness. There's so many things on Windows that are just weird decisions. I'll be using Windows and be like "why the heck did they do it this way?" I'm constantly left scratching my head. Windows has made me lose all respect for Microsoft engineers. They're clearly stupid. On the other hand, everything on Linux makes sense and has good reasoning behind it. You need to learn very little comparatively to understand your entire system.
8. Stability. Not talking about applications/upgrades here, but rather Linux will never crash on you, but I can't go a week without Windows blue screening.
9. Freedom. I like owning my computer. With Windows, Microsoft owns your PC. Does this directly effect everything constantly? Is it the end all reason for me to switch? No, but it's icing on the cake. On Windows I feel stuck and miserable. On Linux I feel free and happy.

I wouldn't ever go back.