When Microsoft boasted yesterday that it sold over 3 million Xbox Ones in 2013, it seemed inevitable that Sony would quickly follow with yelling about its own success. During its CES 2014 keynote today, Sony declared that it had sold-through over 4.2 million PlayStation 4 consoles as of December 28.
Sony launched the PS4 in North America on November 16, then trickled out to more territories over the following weeks. 2.1 million PS4s had been sold by early December, and it evidently kept pace over the holiday season.
Xbox One sales were close to the PS4 at first, but Microsoft's system seems to be slowing down. Which I mention purely for context, certainly not to fuel any sort of dreadful Internet namecalling.