Call me stupid and blind, but for the life of me I couldn't catch the differences in presentation from that video.
It's subtle if you don't know what to look for. My limited understanding is that the PSX rendered polygon vertices at integral pixel coordinates on the screen. The PSX was designed with old SD televisions in mind, so the internal pixel resolution was quite low. When played on an old SD television like was intended, this didn't really look bad. But when you scale the graphics up to higher resolutions, when in motion, polygons suddenly 'jerk' from one PSX pixel to another (which on a high-res display may mean that it jumps quite a few real pixels) with no smooth transition in between. Basically, it's motion rounding error.
It also causes models to distort somewhat since none of the polygons in them really reside in the exact spot where they're supposed to. Again, that wasn't really as noticeable on SD displays, but on high-res displays it's more obvious, especially when combined with motion. If you play a game where the camera pans around and there's a distant model which appears small on the screen, you might notice that the parts of the model seem to scramble all around as the model moves on screen. (Battle scenes on Final Fantasy games where the camera pans around are a good place to look for it.)
