Happy with the PS4 Pro and I must say, most people I know also have PS4's, not a lot of xbox-players out there.
Have Sony and Microsoft released some figures on the sales of their latest consoles?
Now that I finally have both, I think 4K support is going to be fairly hit-and-miss. Games are likely going to have to sacrifice quality elsewhere in order to support 4K & HDR, so the impressions of the consoles might vary a lot depending on which games you compare and what they've sacrificed to keep the frame-rate up.
Xbox One X:
In my experience, games don't have to sacrifice anything noticeable in order to play at 4K (with or without HDR). It's a definite step forward from playing on a 1080p console.
Assassin's Creed Origins: possibly the best looking game I've played. Everything is pin-sharp, HDR is great, framerate is solid.
Dishonoured 2: Not visually spectacular, but I love how everything in the game is so sharp, you can walk up to a book, or a painting inscription, or a poster and read everything without any jaggies.
(Also played Red Dead Redemption, a Xbox 360 game enhanced for Xbox One X. It looks a hell of a lot better than I'd have expected, the game-world geometry (buildings etc.) are slightly simpler/more basic than in more recent games, but the graphics are pin sharp and the frame-rate is fantastic.)
PS4 Pro:
Based on a couple of days' play, it seems games do have to sacrifice a little in order to play at 4K, usually it's the distance at which the LOD reduction kicks in. For me, the PS4 Pro is a must if you move from a 1080p TV to 2160p and want to maintain graphical quality; but it's not a 'WOW' moment.
Witcher 3: Definitely more sky detail and the HDR is great (most noticeably at sunset/sunrise). It seems to me the LOD reduction kicks in much sooner and distance objects lack detail. It might be my imagination, but lighting in some areas seems flat (as if lacking ambient occlusion?). Also noticed the culling of objects behind the player but in front of the camera is very aggressive - often I stepped backwards and a tree suddenly popped into existence behind me.
Battlefield 1: Early mission looks good, though again the distant LOD seems reduced. Once out of the tank and in the narrow confined forrest area, the detail and sharpness of everything was perfect.
GTA V: Only played this briefly, but it didn't seem noticeably better/worse than PS4 on a 1080p screen. Nothing stand-out in the initial play.
I'll definitely be buying any new games on Xbox One X given the choice.