Better framerate and graphics
Bigger hard drive.
Better Wireless Adapter (the OG using non wireless AC was

)
4k (native, checkerboard, and upscaled)
And the ultimately the price just being 100 bucks more.
I can deal with a game like Horizon looking BEAUTIFUL in checkerboarded/faux 4k.
The market spoke that anything more than 400 is suicide and Sony knows better than anyone after the PS3 release. They've never had the most powerful console on the market either in the previous 3 gens outside of the PS3.
But I knew it was a niche system from the jump. Even in the states, there is like 1 pro sold for every 6 to 7 regular PS4s.
It's an option. And most consumers don't care about the shyt that most on here seem to care about. As long as the game looks good "enough", they'll stick to the "regular" PS4 and XB1.
To me, the price of the XBX is not the issue. Granted, those guessing 399 should have never put that out there. Liquid cooling, ultra hd bluray player, and those specs for 399
MS has an exclusive GAMES problem. They are 3 gens in and still haven't gotten it together on that front.