Gaming has been a huge portion of technology since the 1980s, and there has really not been a focus on if low vision gamers could play video games or read text. Now, with built in magnification between operating systems low vision users can finally customize their systems so that text can be read and games can be played, but what OS provides the best experience for gamers who use magnification.
Windows Magnifier has greatly improved over the last few versions of Windows and keeps getting better in Windows 10. You can now magnify in full screen on the Windows Desktop, and in some graphical applications. This will also work while in games, but it will not work in many games that run in full screen. If Magnifier is open and zoomed in while games are open then many games will not function properly.
Zoom on the Mac has been on the Mac for around 10 years and has not had the need to change in that time. Zoom has been the first Desktop magnification solution to allow for full screen and lens style magnification, and it works well in desktop applications and in graphical apps. The really impressive feature of Zoom is that it will work within games that run on the same resolution as the Mac with very minimal effects to performance.
While I prefer the gaming experience that is provided on the Mac, there are still more games available on Windows than there are on the Mac, so the choice of which OS to use as a primary gaming platform will still have to be Windows for the choice of games. The good aspect that Steam provides is that you can buy games from Steam and get the game for both Windows and MacOS.