While I generally come down on the side of the PS4, I do have to chime in on the current sales disparity.
While the PS4 is currently selling "better," it is not selling better by a very large margin. It's stolen a bit of the XBox One's momentum, but both systems sold considerably better than anyone expected. Right now is not the time for Microsoft to panic.
The primary reason for panic over a considerable disparity in install base is developer support. It's the situation that happened with the first two playstation systems. Sony was able to run away with the install base for their systems that they were able to insure development by default. That is the kind of situation that Microsoft and Nintendo need to avoid. If developers abandon their platforms in favor of Sony's hardware, the XBox One will whither and die. Nintendo can limp along with their first-party development for a while, but even they won't be raking in the cash like they used to.
The issue is how much of a disparity is necessary. And I would say that the disparity that Sony would need for an advantage like this is far larger than what currently exists. The PS2 tripled the sales of both it's competitors combined. That's a hefty disparity, and one that the development community wouldn't be able to ignore. The current situation between the XBox One and the PS4 doesn't look like that at all. It isn't even trending in that direction. The PS4 has a respectable lead, but by no means is it overwhelming. And anyone with an appreciation for the history of the industry could have easily predicted this current scenario.
Now is not the time for Microsoft to panic. If Titanfall falls flat, that would be the time to panic. But early reports of the game strongly indicate that Titanfall is going to be quite good. It should help give the XBox One hardware sales a second wind going into the summer, as well as give the 360 a popular title in it's waning years. Titanfall will also likely be a long-tail title, and should still be selling fairly strong throughout the rest of 2014, and into 2015 as well.
The PS4 is benefiting from a late Japanese launch and decent enthusiasm in Europe. And the price disparity is hampering the XBox One now that the holiday spending season is over. That's what's happening here.