For desktop computers, either Windows or Linux. Windows on my main computer since I rely on so much Windows-only software (MS Office, Many Games) despite the BS that Microsoft does to windows in new versions, but Linux has gotten way better lately, especially as it picks up new users as Windows declines. MacOS to me the worst of both worlds when it comes to lack of software support and corporate BS
For Mobile, definitely Android. Android is what I wish Linux was for Desktop computers; Loads of software you can get from many places, open source, and not locked down. It’s mainly the way it is because for Mobile OS’s, Microsoft was spending too much resources shooting itself in the foot with the Zune than to make the necessary improvements to make Windows Mobile to be competitive, and by the time they realized their mistake it was too late. iOS is such a pain in the ass for me to use due to how locked down it is, and while it has more software support than MacOS, its locked down nature and being mostly restricted to getting software from Apple means that several apps that I rely on (including a few apps not on the Google Play store) will never be available for iOS. I also like to see where every single file on my phone actually is
For desktop I’m a Linux or macOS guy. I use Fedora Workstation on my main laptop because it’s been damn stable while also being up-to-date, and I like the workflow of GNOME and the flexibility Linux offers (experimenting with tiling windows managers is a recent example). I have an old MacBook with OCLP for easy access to creative software like Adobe and Ableton etc, but I find macOS takes a lot more configuration to make it comfortable – it’s not a perfect OS and it’s no privacy bastion, but it sure beats Windows. I also have a relatively powerful Windows laptop I used for gaming (yes I agree, not the best choice), but I’m using it more rarely since only a few games with anticheat keep Windows necessary. I’ve just always felt like I have to actively fight Windows to get work done, its automatic updates are way more intrusive than they need to be; it’s annoying as hell to be playing a game when suddenly the system decides it wants to download updates right now, tanking my network performance.
In the mobile world I tend to prefer Android of really any variety just because it doesn’t pretend it’s not a computer: file managers aren’t as underpowered here as they were on iOS last I tried. More than ever I’m in the Android camp now that software update guarantees are more reasonable, and the whole texting between iPhones thing is much better after iOS 18. I’m not opposed to an iPhone in the future since they do still have great software support and iOS is somewhat more customizable now, but I’ll probably sooner get a solid Android phone to run CalyxOS or GrapheneOS, that’s my ideal outcome.
Honestly, aside from Windows 11 and its insanely inconsistent/unpolished UX and awful AI integrations, operating systems have been pretty damn good lately. This opinion mostly coincides with modern desktop Linux being such a joy to use now that I’ve found what I like, things are stable and modern, and it’s just not as annoying as Windows.