Without antialiasing the picture looks crisp and clear and it has perfect contrast between an item and its surroundings or between two adjacent colors. But the larger the pixels the rougher it looks because you can clearly see every pixel. In retina or ultra high density or whatever it’s called monitor or display you don’t see pixels so you don’t need antialiasing for CAD programs or text editors etc. which use clear lines and other graphic items against clear background.
Seeing pixels may not bother you in CAD programs. Actually it may even be beneficial when you e.g. want to see if a line is exactly horizontal/vertical/45deg. You can see some sharp pixels in the middle of the line if it’s not. That would be distracting in a game and that’s one reason why antialiasing is used in them.
For a CAD program it’s important to see the same size as same everywhere. That was a problem when eeschema moved to the “modern” graphics canvas some months ago. When you have a two wires they should look the same no matter where they are and in which position. But it’s difficult to make them so for example if the view is zoomed out and there are several lines close to each other. It needs an algorithm to decide how they should be rendered. Antialiasing may help here but it always makes the view blurry because it mixes a pixel with its surrounding pixels.
But the story is different for games. You just can’t compare 3D games and CAD programs. Games have moving graphics and they try to mimic real world looks (more or less). It’s annoying to see sharp edges and pixels especially when the picture changes. It’s not important to have clear lines but have smooth overall experience without distracting pixel-sized details.
When you try antialiasing for a CAD program the result may look blurry. Different antialiasing settings work differently and the differences may look clearer than in games.
Furthermore, different settings work differently with different monitors/displays. For example I have in KDE font settings the option Sub-pixel rendering type. The options are: Horizontal RGB and BGR and vertical RGB and BGR. That’s because displays can have their physical pixel’s subpixels (red, green, blue) in different order.
The quality vs. speed doesn’t matter for KiCad. It matters for games where the 3D graphics acceleration reaches its speed limits under heavy load.
In short, it’s different for games and for CAD, drawing, fonts etc. You can’t compare them. And there’s no one best option for all users and all situations. I prefer no antialiasing.