But people here are saying that "quality degrades with scaling", "native resolution was a fail" for them, and "you don't want to scale unless it's racing games and stuff with little text."
This is a zombie thread from 2012 - before the 5k iMac and before - or in the very early days of - the Retina MacBook Pro. Retina/4k/5k displays and newer versions of MacOS have changed the game.
On a "standard def" LCD monitor the best results by far come from driving it at native resolution. Circa 2012, "scaling" means that the computer outputs a lower-res signal and the
monitor zooms it to fill the screen. The result is pretty awful unless - as you say - it is a movie or game with no text or "hard edges".
With a Retina/4k/5k display in so-called "HiDPI" mode, however, a Mac will
always drive the display at native resolution - even in the so-called "scaled" modes - and the system uses various scaling and re-sampling techniques to produce a display that "looks like" the scaled resolution in terms of text and icon sizes, produces a passable result for older applications, but still allows modern "Retina-aware" applications to use something like the full native resolution of the display. (You can look up the gory details of HiDPI and 'scaled mode' if you like).
Suffice to say the results are good enough that the new MBPs default to a non-native "scaled" screen mode.
As for Windows: it's technically more flexible in that - since
forever - you've been able to change the "DPI" value to match the display and
properly written applications will query the operating system whenever they need to convert between pixels and 'real' dimensions or create a bitmap for off-screen rendering. On Win10, you can set the "magnification" for each screen connected to the system. In practice, though, it is very dependent on the mythical "properly written" application - especially when it comes to the magnification changing "on the fly" (e.g. dragging a window between a standard res and 4k screen). My experience is that it
certainly can't cope on a laptop that gets moved between different external screen setups - and I'd often be presented with a window with either huge or tiny text and icons. The Apple way sounds a bit kludgey but is more robust in the face of multiple, mixed displays and old apps.