PS4 can do 1080p. Xbox One can't in many cases.
That's what the debate is about. It's about people downplaying PS4s power advantage by saying it doesn't matter, which it clearly does as it leads to better resolution and framerate.
Whether you can notice the difference doesn't matter. People like buying the more powerful console especially if its also the most popular. This resolution difference made a lot more sense when XB1 was $500 and PS4 was $400. You were basically paying a lot more for an technically inferior product.
I don't know why the debates are still going on though. 1080p > 720p. PS4 > Xbox One. These are facts that aren't going to ever change.