Sony’s PlayStation Vita portable gaming system made its debut in Japan on Saturday and early sales estimates are beginning to trickle out. According to research firm Enterbrain, Sony sold 321,400 Vita units during the first 48 hours of the device’s availability. That’s 50,000 fewer units than Nintendo sold after the 3DS made its debut in the country. Nintendo ran into trouble shortly after launch as consumer interest in the 3DS faded due to a lack of compelling games, and the company eventually had to drop the price of its system to regain momentum. We first went hands-on with the PlayStation Vita during E3 2011 and, while it was still an early build of the device, we really liked the form factor and impressive graphics. Sony is expected to launch the Vita in North America and Europe in February for $250, and a 3G-enabled version should launch in the United States in partnership with AT&T around the same time.