Games
Neither the Xbox One S nor the PS4 Slim are “new” consoles. They’re just smaller, slightly updated versions of the consoles you already know. That means the game libraries are exactly the same. If you already had a certain preference, that basically carries over to these newer iterations of hardware.
If Halo, Gears of War, and Forza are more your thing, then the Xbox One S has your name written all over it. Alternatively, if you’re a sucker for Naughty Dog games, want a wider selection of Japanese offerings, or are into any other Sony exclusives, then the PS4 Slim is waiting patiently for you to pick it up. There are third-party partnerships to consider as well. Sony has a solid thing going with Destiny and Call of Duty, while Microsoft and EA have been rubbing shoulders a lot lately.
Nobody knows what you prefer better than you, so go with what you love if you’re finding it difficult to make a choice.