In addition to what
@Dantte already said, a higher resolution means less reliance on AA, and therefore a simplified rendering pipeline and less potential for side effects (like how Saints Row 3 supports AA for geometry, but not for transparent textures, which just looks ridiculous).
Playing on a 27" 4K screen, I still notice aliasing in 4K. It's no longer as distracting as it used to be when I still played in 1080p, but it's still far from perfect. If I can buy a decent 27" 8K gaming screen, I will. I don't need other people telling me what I can or can't see, thank you very much.