You honestly can't tell the drop in resolution. What you DO notice is some of the sacrifices made to hit 60 fps. Such as shadows for buildings and such drawing in as you get close or the world getting more detailed as you approach it. Halo 5 still manages to be one of the best looking games to date. And really 60 fps is not the only reason they had to make sacrifices. Campaign spaces were twice as big as normal. More enemies per area then any halo game to date. 4 Spartans on the field at all times with seemless drop in and out. They made the campaign bigger and more dynamic to sell a true coop experience. And that is also why sacrifices were made. Call of duty easily hits 60 fps on both systems. Because they downgrade the hell out of visual fidelity. It's not the system struggling. It's what the devs do with what is available.

I notice. It's more apparent on a larger screen then let's say a competition can size 21" I think most gamers who compete wouldn't notice on a smaller screen with a 1ms refresh rate. Pixel are too small.