Regardless of current technology, the undeniable fact is that 4k has a higher data throughput. More data results in (ideally) a clearer video. Obviously, on a 1080p monitor a 1080p data stream will dictate every single pixel and thus have an absolutely undistorted image. 'Upgrading' that data stream to 4K will make it run the video through a resizing algorithm, and while downsizing algorithms are far superior to upsizing algorithms, it will cause some data distortion.
