Both XBOX and PlayStation next gen are going to be very similar. They're using the same basic specs of hardware from AMD. The differences will only be in details like RAM configuration and storage space, and things like that. They're going to be practically the same, the main difference will be the games — like it always has been. Whoever has the most entertaining lineup of exclusive games will be the leader. This is why Microsoft went crazy buying talent and studios.
This is basically 2013 all over again, when XBOX One and PS4 both launched with similar hardware and only difference being PS4 used GDDR 5 RAM as opposed to XBOX One using GDDR4 which made a difference — games technically ran slightly better on PS4 at the time.
But like I said, the difference will always come down to the games. Currently PlayStation has been leading in exclusive games. Microsoft is going to need to put out more than just Halo, Gears, and Forza to attract consumers.