Well, what do you know? One of the most impressive games shown thus far is native 1080p at 60fps on both systems. And, no, I don't think there's anything wrong with why the Xbox One version wasn't shown.
Personally, I'm thinking a marketing deal of some kind. I know Mortimer says that's not the case, but I think that's underestimating how aggressively Sony is marketing the PS4. When they say that the PS4 marketing campaign is the largest in Sony's history, they probably aren't just dishing out hyperbole. Even I made a thread on how much I think the PS4 marketing is outpacing the Xbox One marketing thus far, at least from what I've seen on US television, and how much it surprised me. But it doesn't just stop there, folks.
Pay special attention to what Sony is doing. They appear to be doing more third party publisher/game specific deals now than I've ever seen them do before. Look at the big marketing campaign around Watch Dogs before it was pushed back, look at the way Assassin's Creed has gotten a spotlight on the system. That new Assassin's Creed US TV commercial with Drake's 'started from the bottom' opens up with the playstation logo and ends only showing the game coming for the PS4 and PS3. You've got things like exclusive additional gameplay, exclusive DLC, and it spreads across multiple games, even Destiny.
Before the first footage of the next gen version of this game was ever shown, it was officially labeled by the company making it as the debut of the first PS4 footage. That's not something you commonly see without some type of deal in place. They usually just say instead that you're seeing the next gen console version of the game for the first time, but it was highlighted as the PS4 version. Or am I mistaken about the company themselves saying that? Was it someone else who called it the PS4 version before the footage was ever shown, and not 2K themselves? Either way, doesn't matter, I suppose, but, trust me, if I even remotely catch wind that the Xbox One version isn't perfectly up to snuff, I can always cancel my pre-order for the game, and just grab the PS4 version later. I've got plenty of time to do that before the system launches, and the game has to be reviewed, on both versions, before the PS4 is out, since the game also launches with the PS4.