Hard-core videogame players typically are loyal to either PlayStation or Xbox. Until last year, Mario Valdes was an Xbox guy.

But in November—when Microsoft Corp. released its new Xbox One console and Sony Corp., its PlayStation 4—he made a switch. In his mind, Microsoft's $499 console, which came with a motion and voice-sensing accessory called Kinect, didn't compare well with Sony's $399 system without an equivalent feature.

"I...