My reasons were plain and simple.
I wanted a gaming console, not a Kinect-optimized piece of kit that had too much system reserve for motions and gestures that officially forced Microsoft to adjust this decision.
The PS4 did not have a mandatory add-on for a camera - Not the smartest move. It is also £79 more expensive as a result of this. The frames per second issue with having to run certain games at 720p to hit 60fps was a put off for the Xbox One also.
Gran Turismo is one of my favourite games which is also exclusive to Playstation.
The PS4 design is much more slick and compact. It does not require a large external powerpack. It's got a Playstation Now service which I don't believe Microsoft have an answer for. The joypad is brilliant and interactive.
You can swap the internal 500gb hard drive for a 1TB Solid State Hybrid Drive allowing for double the capacity of the lock-in Xbox One hard drive.
Microsoft have marketed the Xbox One as an all-rounder where as the PS4 is a gaming console. You are likely to see Microsoft Office hit the Xbox One which again is a multi-task option where as the PS4 is still designed for hardcore gaming.
GDDR5 Graphics RAM was used against DDR3 of the Xbox. It is a far more powerful console than the Xbox One.
I could keep going but I believe the PS4 is much better value for money, cheaper, more powerful, no mandatory add-ons...need I say more?