At the moment there is no real "winner". I'd say Xbox One has the best exclusives right now, as well as the best looking game in Ryse, but at the moment even the Wii U has a better library so...not really much good to say about either system right now. Infamous Second Son is the first genuinely great PS4 game I've played, but it's also quite short for an open world game, and after the campaign is done there really isn't much to do, especially if you made taking out DUP bases a priority during the actual campaign. Knack is bleh and Killzone Shadowfall is okay, and in terms of digital offerings Resogun is okay but gets old pretty quickly. On the One there's Dead Rising 3, which remains one of my favorite games between the two systems despite some difficulty issues. There's also Ryse which is more fun then I thought it would be, and fills the role of glorified retail tech demo much better then Knack does. Finally, there's also Forza Motorsport, which is a fun racing game for casual racing fans like myself. Overall, there's just more meat and polish to the One games as opposed to the PS4 line up.
I think the eventual winner will obviously be the PS4, though. It's upcoming library looks more appealing, and it's dominance in the market place ought to guarantee a slew of excellent exclusives, especially from Japan. So if you ABSOLUTELY NEED one of these consoles now, PS4 is probably the best long term investment. Just prepare to let it gather dust for awhile once you've played through the few fun games currently on the system.
Frankly, the Vita and 3DS are both much better purchases right now. Vita is especially vital for prospective PS4 owners.