My cousin didnt see a difference on my new PS4 Pro. But I was amazed by the difference!

[dgboweniii]

It's because you just wasted $400 bucks and and you're seeing what you want to see.  ANY improvement you see is from the 4k set, and as others have said, to the human eye there hardly is going ro be a difference with 4k.  It's much more about HDR than res.