By all accounts Microsoft’s Xbox One has sold very well so far but there have been some indications that it’s already fallen behind sales of Sony’s PlayStation 4. Forbes contributor Paul Tassi notes that after Sony announced that PS4 sales were up to 2.1 million last week, Microsoft responded by… talking about how many hours gamers have spent playing Xbox One games. Microsoft’s silence on the latest sales figures follows reports that the PlayStation 4 is outselling the Xbox One in the United Kingdom and polls showing that more gamers plan to buy a PlayStation 4 over the Xbox One during the holiday shopping season.

When looking for reasons why Xbox One sales may be lagging behind the PlayStation 4, the most obvious place to start is with the $100 price difference between the consoles. The major reason the Xbox One costs $100 more than the PS4 is the mandatory inclusion of its next-generation Kinect sensor that Microsoft is betting will pay big dividends down the line as more gamers clamor for voice and gesture controls. Microsoft is also pushing the Kinect as a major benefit for advertisers since it can track users’ facial expressions during commercials and give marketing firms real-time feedback on their work.

The big issue so far, as Tassi notes, is that Microsoft hasn’t yet figured out a way to make the Kinect valuable enough to gamers where they’re willing to shell out an extra $100 to get it. While voice and gesture commands are nice options, most gamers still rely on controllers as their primary method of playing. Tassi also says that the games Microsoft released to show off the next-generation Kinect’s abilities haven’t been well received so far, which is something Microsoft will certainly have to work on if it wants the Kinect to be a must-have for gamers.

“I just can’t find support for the argument that Kinect 2.0 has given Microsoft an edge over Sony,” Tassi concludes. “Perhaps it adds some value to the Xbox One, but $100 or more worth? I don’t think so. Take away Kinect, and you have two $400 system that are more or less equivalent. PS4 might have a slight edge in power, but I think Xbox One has a better launch line-up with the promise of more good exclusives on the horizon (Titanfall). But with Kinect, an increased price for not enough value might be all some consumers see.”