I had the same decision to make last year. I ended up picking a PS4 as at the time, the xbox was an always on device, with a constant network connection and had a camera attached to it at all times to work (the kinnect). This in a child’s bedroom did not seem right.
Combined with their desire to cash in on 2nd hand games market (you have to pay to transfer license for pre-owned game) as well as the fact that ps4 was cheaper was what swayed me in the end.
* Edited for spelling as typing on phone is a pain in the ass.