I'm noticing a huge difference compared to when I played this on the PS4, both graphically and even the sound quality with my speakers. During the first mission, I could hear the guitar playing off in the distance from the O'Driscoll's camp at Sadie's homestead, which I never noticed on the console.
The snow is deeper, you can see the urine near the horse hitches, taller grass, improved draw distance, etc... little details like that make it feel technologically ahead. The new content will be interesting to experience as well.