Well I bought the xb1 X last week and I am bit disappointed as well because I don't see that much d8fference between the pro and X. I am still glad I will be able to play some games at 60fps such as gears 4 which IMO looks better at 1080p 60fps than 4k 30fps. It is my bad because I expected more on native 4k or maybe my eyes got used to higher resolution. I bought the witcher 3 to play it at 60fps as well since again, native 4k doesn't look that impressive to me. I do have a 4ktv with hdr.
Well that always depends how far you're sitting away from the screen.
When I play a 4k game, I usually sit directly in front of my 70" TV. (just a bit over 1m). For anything else (FullHD content) I sit on my couch which is roughly 3m away from screen.
even then, don't expect the difference to be massive if you compare 4k to whatever PS4 Pro usually renders at.