In my perspective and personal account, the media, retail companies and gaming outlets REALLY wanted Microsoft's Xbox One to be the winner - even after sales statistics and forecasts clearly showed that the PS4 was outselling the X1 two to one.
The X1 is obviously an American product (Microsoft) but E3's 2013 shit show DRM controversy totally f**ed them. I remember that demonstration, that whole keynote was about TV, Cable, Football and Kinect. Videogames was clearly an afterthought for Microsoft and everyone saw it. Microsofts stock took a dive and gamers crucified it's marketing pitch - which was completely justified. The PS4 is for gamers.
Bold: Media didn't push XB1 more than PS4 from my memory. They saw everyone's reaction to the XB1 reveal and often they decided that there was money in supporting the critical narrative. For instance:
Though talking retail sellers (or at least Gamestop), I kinda see your point. Even here in Denmark, Gamestop has (almost every month since 2014) been begging me to trade in my PS4 towards an XB1 and later XB1X. Often they don't have (or at least don't advertise) the option to trade in my XB1 towards a PS4.
But I don't think they're biased. I rather think they're being compensated in some way. It's just business, I guess.